diff --git a/gpx-rs/engine/src/core/algorithm/timestamps.rs b/gpx-rs/engine/src/core/algorithm/timestamps.rs
index 08c0e1bd5..f18e743e1 100644
--- a/gpx-rs/engine/src/core/algorithm/timestamps.rs
+++ b/gpx-rs/engine/src/core/algorithm/timestamps.rs
@@ -82,6 +82,38 @@ pub fn replace_trackpoints(
     trkpt.splice(start..end, points);
 }
 
+/// How long each interval between two consecutive trackpoints of a segment should last, relative
+/// to the others, for a made-up pace: the longer the interval, and the steeper it goes up, the
+/// longer. `slopes` has the slope (in %) at each trackpoint.
+pub fn artificial_weights(points: &[Trackpoint], slopes: &[f64]) -> Vec<f64> {
+    points
+        .windows(2)
+        .zip(slopes)
+        .map(|(pair, slope)| {
+            let km = distance(pair[0].coordinates, pair[1].coordinates);
+            km * (0.5 + 1.0 / (1.0 + (-0.2 * slope).exp()))
+        })
+        .collect()
+}
+
+/// `points` with made-up timestamps: the first one is at `start`, and each next one follows the
+/// previous one after `weights[i]` times `ms_per_weight` milliseconds (see [`artificial_weights`]).
+pub fn with_artificial_timestamps(
+    mut points: Vec<Trackpoint>,
+    weights: &[f64],
+    ms_per_weight: f64,
+    start: i64,
+) -> Vec<Trackpoint> {
+    let mut elapsed = 0.0;
+    for (i, point) in points.iter_mut().enumerate() {
+        if i > 0 {
+            elapsed += weights[i - 1] * ms_per_weight;
+        }
+        point.time = Some(start + elapsed as i64);
+    }
+    points
+}
+
 fn same_place(a: &Trackpoint, b: &Trackpoint) -> bool {
     a.coordinates.lng == b.coordinates.lng && a.coordinates.lat == b.coordinates.lat
 }
@@ -111,7 +143,7 @@ fn timestamp_after(a: &Trackpoint, b: &Trackpoint, speed: Option<f64>) -> Option
 ///
 /// Unlike the old code, a `last` without a time does not get `start_time` itself, only the copy
 /// used here.
-fn with_timestamps(
+pub fn with_timestamps(
     points: Vec<Trackpoint>,
     speed: Option<f64>,
     last: Option<&Trackpoint>,
@@ -141,7 +173,7 @@ fn with_timestamps(
 /// `points` with their timestamps moved so that the first one follows `last`, and their durations
 /// multiplied by `ratio`. The ones that have no timestamp follow the previous one, as in
 /// [`with_timestamps`]. Without a time for `last`, or for the first point, none is known.
-fn shifted_and_compressed(
+pub fn shifted_and_compressed(
     points: Vec<Trackpoint>,
     speed: Option<f64>,
     ratio: f64,
diff --git a/gpx-rs/engine/src/engine/command/tools/time.rs b/gpx-rs/engine/src/engine/command/tools/time.rs
index 722072dba..fe9b73547 100644
--- a/gpx-rs/engine/src/engine/command/tools/time.rs
+++ b/gpx-rs/engine/src/engine/command/tools/time.rs
@@ -1,11 +1,255 @@
-use crate::{Apply, CommandError, State};
+use std::rc::Rc;
 
+use crate::{
+    Apply, CommandError, File, SegmentLocation, State, Statistics, TrackSegment, Trackpoint, artificial_weights,
+    shifted_and_compressed, with_artificial_timestamps, with_timestamps,
+};
+
+/// How the timestamps of the selection are set.
+#[derive(Debug, Clone, Copy)]
+pub enum TimeKind {
+    /// Starts at `Time::start_time`. The trackpoints that have timestamps keep their durations
+    /// multiplied by `ratio`, and the ones that have none follow the previous one at `speed`
+    /// (km/h).
+    Change { speed: f64, ratio: f64 },
+    /// Makes timestamps up for the whole selection, which lasts `total_time` seconds: the longer
+    /// and the steeper an interval, the more time it takes.
+    Artificial { total_time: f64 },
+}
+
+/// Sets the timestamps of the selected segments, one after the other: each one goes on from the
+/// end of the previous one, the first one starts at `start_time` (in milliseconds).
 #[derive(Debug)]
-pub struct Time;
+pub struct Time {
+    pub start_time: i64,
+    pub kind: TimeKind,
+}
 
 impl Apply for Time {
-    fn apply(self, _state: &mut State) -> Result<(), CommandError> {
-        // TODO
-        Err(CommandError::NotImplemented("time"))
+    fn apply(self, state: &mut State) -> Result<(), CommandError> {
+        match self.kind {
+            TimeKind::Change { speed, ratio } => {
+                if !(speed.is_finite() && speed > 0.0 && ratio.is_finite() && ratio > 0.0) {
+                    return Err(CommandError::InvalidData(format!(
+                        "speed {speed} and ratio {ratio} should be positive"
+                    )));
+                }
+            }
+            TimeKind::Artificial { total_time } => {
+                if !(total_time.is_finite() && total_time >= 0.0) {
+                    return Err(CommandError::InvalidData(format!(
+                        "total time {total_time} should not be negative"
+                    )));
+                }
+            }
+        }
+
+        let locations = state
+            .selection
+            .segment_locations(state.files, &state.order.0);
+        let segment_at = |location: &SegmentLocation| -> &TrackSegment {
+            &state.files[&location.file_id].trk[location.trk].trkseg[location.seg]
+        };
+        if locations.iter().all(|location| segment_at(location).is_empty()) {
+            return Err(CommandError::NothingToDo);
+        }
+
+        // the new timestamps of each segment
+        let mut times: Vec<Vec<Option<i64>>> = Vec::with_capacity(locations.len());
+        match self.kind {
+            TimeKind::Change { speed, ratio } => {
+                let mut last: Option<Trackpoint> = None;
+                for location in &locations {
+                    let points: Vec<Trackpoint> = segment_at(location).iter().cloned().collect();
+                    let Some(first) = points.first() else {
+                        times.push(vec![]);
+                        continue;
+                    };
+                    let start = last.clone().unwrap_or_else(|| {
+                        let mut start = first.clone();
+                        start.time = Some(self.start_time);
+                        start
+                    });
+                    let points = if first.time.is_none() {
+                        with_timestamps(points, Some(speed), Some(&start), Some(self.start_time))
+                    } else {
+                        shifted_and_compressed(points, Some(speed), ratio, &start)
+                    };
+                    last = points.last().cloned();
+                    times.push(points.iter().map(|point| point.time).collect());
+                }
+            }
+            TimeKind::Artificial { total_time } => {
+                let mut weights: Vec<Vec<f64>> = locations
+                    .iter()
+                    .map(|location| {
+                        let segment = segment_at(location);
+                        let points: Vec<Trackpoint> = segment.iter().cloned().collect();
+                        let stats = Statistics::compute(segment);
+                        let slopes: Vec<f64> = stats.local.iter().map(|l| l.slope).collect();
+                        artificial_weights(&points, &slopes)
+                    })
+                    .collect();
+                let mut total: f64 = weights.iter().flatten().sum();
+                if !(total > 0.0) {
+                    // no distance to share the time by: every interval takes as long
+                    for weights in &mut weights {
+                        weights.iter_mut().for_each(|w| *w = 1.0);
+                    }
+                    total = weights.iter().map(Vec::len).sum::<usize>() as f64;
+                }
+                let ms_per_weight = if total > 0.0 {
+                    total_time * 1000.0 / total
+                } else {
+                    0.0
+                };
+
+                let mut start = self.start_time;
+                for (location, weights) in locations.iter().zip(&weights) {
+                    let points: Vec<Trackpoint> = segment_at(location).iter().cloned().collect();
+                    if points.is_empty() {
+                        times.push(vec![]);
+                        continue;
+                    }
+                    let points = with_artificial_timestamps(points, weights, ms_per_weight, start);
+                    // the next segment goes on from the end of this one
+                    start = points.last().and_then(|point| point.time).unwrap_or(start);
+                    times.push(points.iter().map(|point| point.time).collect());
+                }
+            }
+        }
+
+        // the segments of a file are consecutive
+        let mut times = times.into_iter();
+        for group in locations.chunk_by(|a, b| a.file_id == b.file_id) {
+            let file_id = group[0].file_id;
+            let mut file: File = (*state.files[&file_id]).clone();
+            for location in group {
+                let times = times.next().unwrap_or_default();
+                let segment = &mut file.trk[location.trk].trkseg[location.seg];
+                segment.update_all(|i, pt| pt.time = times.get(i).copied().flatten());
+                segment.rev_id = Default::default();
+            }
+            state.files.insert(file_id, Rc::new(file));
+        }
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::HashSet;
+
+    use crate::{FileId, Load, Selection, engine::command::fixture::Fixture};
+
+    use super::*;
+
+    fn loaded(path: &str) -> (Fixture, FileId) {
+        let mut fx = Fixture::default();
+        let data = std::fs::read(path).unwrap();
+        Load {
+            data: &data,
+            name: "file",
+        }
+        .apply(&mut fx.state())
+        .unwrap();
+        let id = fx.order.0[0];
+        fx.selection = Selection::File {
+            file_ids: HashSet::from([id]),
+        };
+        (fx, id)
+    }
+
+    fn all_times(fx: &Fixture, id: FileId) -> Vec<Option<i64>> {
+        fx.files[&id]
+            .trk
+            .iter()
+            .flat_map(|trk| trk.trkseg.iter().flat_map(|seg| seg.iter().map(|pt| pt.time)))
+            .collect()
+    }
+
+    #[test]
+    fn test_artificial_timestamps_last_the_total_time() {
+        let (mut fx, id) = loaded("data/with_tracks_and_segments.gpx");
+
+        Time {
+            start_time: 1_000_000,
+            kind: TimeKind::Artificial { total_time: 3600.0 },
+        }
+        .apply(&mut fx.state())
+        .unwrap();
+
+        let times: Vec<i64> = all_times(&fx, id).into_iter().map(Option::unwrap).collect();
+        assert_eq!(times[0], 1_000_000);
+        assert!(times.windows(2).all(|w| w[0] <= w[1]));
+        assert!((times.last().unwrap() - 1_000_000 - 3_600_000).abs() <= times.len() as i64);
+    }
+
+    #[test]
+    fn test_change_starts_at_the_start_time_and_follows_the_speed() {
+        let (mut fx, id) = loaded("data/simple.gpx");
+        Time {
+            start_time: 5_000,
+            kind: TimeKind::Change {
+                speed: 10.0,
+                ratio: 1.0,
+            },
+        }
+        .apply(&mut fx.state())
+        .unwrap();
+
+        let times: Vec<i64> = all_times(&fx, id).into_iter().map(Option::unwrap).collect();
+        assert_eq!(times[0], 5_000);
+        assert!(times.windows(2).all(|w| w[0] <= w[1]));
+        assert!(times.last() > times.first());
+    }
+
+    #[test]
+    fn test_change_shifts_existing_timestamps_and_scales_them() {
+        let (mut fx, id) = loaded("data/with_time.gpx");
+        let before: Vec<i64> = all_times(&fx, id).into_iter().map(Option::unwrap).collect();
+
+        Time {
+            start_time: 0,
+            kind: TimeKind::Change {
+                speed: 10.0,
+                ratio: 2.0,
+            },
+        }
+        .apply(&mut fx.state())
+        .unwrap();
+
+        let after: Vec<i64> = all_times(&fx, id).into_iter().map(Option::unwrap).collect();
+        assert_eq!(after[0], 0);
+        let (d_before, d_after) = (before[1] - before[0], after[1] - after[0]);
+        assert!((d_after - 2 * d_before).abs() <= 1);
+    }
+
+    #[test]
+    fn test_invalid_input_and_empty_selection() {
+        let (mut fx, id) = loaded("data/simple.gpx");
+        let before = all_times(&fx, id);
+        assert!(matches!(
+            Time {
+                start_time: 0,
+                kind: TimeKind::Change {
+                    speed: 0.0,
+                    ratio: 1.0
+                }
+            }
+            .apply(&mut fx.state()),
+            Err(CommandError::InvalidData(_))
+        ));
+        assert_eq!(all_times(&fx, id), before);
+
+        fx.selection = Selection::Empty;
+        assert!(matches!(
+            Time {
+                start_time: 0,
+                kind: TimeKind::Artificial { total_time: 10.0 }
+            }
+            .apply(&mut fx.state()),
+            Err(CommandError::NothingToDo)
+        ));
     }
 }
diff --git a/gpx-rs/wasm/src/lib.rs b/gpx-rs/wasm/src/lib.rs
index 7651011e6..f0e35c976 100644
--- a/gpx-rs/wasm/src/lib.rs
+++ b/gpx-rs/wasm/src/lib.rs
@@ -613,9 +613,25 @@ pub fn split(revision: u32, at: u32, split_type: SplitType) -> bool {
         }))
 }
 
-#[wasm_bindgen]
-pub fn time() -> bool {
-    edit(Command::Time(engine::Time))
+/// Sets the timestamps of the selection, which starts at `start_time` (ms since the epoch): the
+/// trackpoints that have some keep their durations multiplied by `ratio`, the others follow the
+/// previous one at `speed` (km/h).
+#[wasm_bindgen(js_name = changeTimestamps)]
+pub fn change_timestamps(start_time: f64, speed: f64, ratio: f64) -> bool {
+    edit(Command::Time(engine::Time {
+        start_time: start_time as i64,
+        kind: engine::TimeKind::Change { speed, ratio },
+    }))
+}
+
+/// Makes up timestamps for the selection, which starts at `start_time` (ms since the epoch) and
+/// lasts `total_time` seconds.
+#[wasm_bindgen(js_name = createArtificialTimestamps)]
+pub fn create_artificial_timestamps(start_time: f64, total_time: f64) -> bool {
+    edit(Command::Time(engine::Time {
+        start_time: start_time as i64,
+        kind: engine::TimeKind::Artificial { total_time },
+    }))
 }
 
 /// Merges the selection into its first element (see `MergeType`). `remove_gaps` brings the parts
diff --git a/website/src/lib/components/Menu.svelte b/website/src/lib/components/Menu.svelte
index a39f0561c..afcfc2d53 100644
--- a/website/src/lib/components/Menu.svelte
+++ b/website/src/lib/components/Menu.svelte
@@ -63,7 +63,6 @@
     import { engine } from '$lib/engine';
     import { allHidden } from '$lib/all-hidden';
     import { selectionSize } from '$lib/selection-helpers';
-    // TODO centering on the selection still works on the previous implementation
     import { boundsManager } from '$lib/logic/bounds';
     import { onMount } from 'svelte';
 
diff --git a/website/src/lib/components/file-list/style/StyleDialog.svelte b/website/src/lib/components/file-list/style/StyleDialog.svelte
index 5f886ca92..89866be0d 100644
--- a/website/src/lib/components/file-list/style/StyleDialog.svelte
+++ b/website/src/lib/components/file-list/style/StyleDialog.svelte
@@ -33,7 +33,6 @@
     let opacityChanged = $state(false);
     let widthChanged = $state(false);
 
-    // TODO the inputs used to come from the last selected item, they now come from this node
     function setStyleInputs() {
         opacity = $defaultOpacity;
         width = $defaultWidth;
diff --git a/website/src/lib/components/toolbar/tools/Time.svelte b/website/src/lib/components/toolbar/tools/Time.svelte
index 1bf2d5797..a5ea5ce86 100644
--- a/website/src/lib/components/toolbar/tools/Time.svelte
+++ b/website/src/lib/components/toolbar/tools/Time.svelte
@@ -15,23 +15,19 @@
     import { CalendarClock, CirclePlay, CircleStop, CircleX, Timer, Zap } from '@lucide/svelte';
     import { untrack } from 'svelte';
     import { i18n } from '$lib/i18n.svelte';
-    import {
-        ListFileItem,
-        ListRootItem,
-        ListTrackItem,
-        ListTrackSegmentItem,
-    } from '$lib/components/file-list/file-list';
     import Help from '$lib/components/Help.svelte';
     import { getURLForLanguage } from '$lib/utils';
-    import { selection } from '$lib/logic/selection';
     import { settings } from '$lib/logic/settings';
-    import { fileActionManager } from '$lib/logic/file-action-manager';
-    import { gpxStatistics } from '$lib/logic/statistics';
+    import { engine } from '$lib/engine';
 
     let props: {
         class?: string;
     } = $props();
 
+    const selection = engine.selection;
+    const statistics = engine.statistics;
+    let global = $derived($statistics.global);
+
     let startDate: DateValue | undefined = $state(undefined);
     let startTime: string | undefined = $state(undefined);
     let endDate: DateValue | undefined = $state(undefined);
@@ -59,26 +55,28 @@
     }
 
     function setGPXData() {
-        if ($gpxStatistics.global.time.start) {
-            startDate = toCalendarDate($gpxStatistics.global.time.start);
-            startTime = toTimeString($gpxStatistics.global.time.start);
+        if (global.startTime !== undefined) {
+            const start = new Date(global.startTime);
+            startDate = toCalendarDate(start);
+            startTime = toTimeString(start);
         } else {
             startDate = undefined;
             startTime = undefined;
         }
-        if ($gpxStatistics.global.time.end) {
-            endDate = toCalendarDate($gpxStatistics.global.time.end);
-            endTime = toTimeString($gpxStatistics.global.time.end);
+        if (global.endTime !== undefined) {
+            const end = new Date(global.endTime);
+            endDate = toCalendarDate(end);
+            endTime = toTimeString(end);
         } else {
             endDate = undefined;
             endTime = undefined;
         }
-        if ($gpxStatistics.global.time.moving && $gpxStatistics.global.speed.moving) {
-            movingTime = $gpxStatistics.global.time.moving;
-            setSpeed($gpxStatistics.global.speed.moving);
-        } else if ($gpxStatistics.global.time.total && $gpxStatistics.global.speed.total) {
-            movingTime = $gpxStatistics.global.time.total;
-            setSpeed($gpxStatistics.global.speed.total);
+        if (global.movingTime && global.movingSpeed) {
+            movingTime = global.movingTime;
+            setSpeed(global.movingSpeed);
+        } else if (global.totalTime && global.totalSpeed) {
+            movingTime = global.totalTime;
+            setSpeed(global.totalSpeed);
         } else {
             movingTime = undefined;
             speed = undefined;
@@ -86,7 +84,7 @@
     }
 
     $effect(() => {
-        if ($gpxStatistics && $velocityUnits && $distanceUnits) {
+        if ($statistics && $velocityUnits && $distanceUnits) {
             untrack(() => setGPXData());
         }
     });
@@ -102,16 +100,23 @@
         return new Date(date.year, date.month - 1, date.day, hours, minutes, seconds);
     }
 
+    /** Total time over moving time. */
+    function timeRatio() {
+        return global.movingTime && global.totalTime ? global.totalTime / global.movingTime : 1;
+    }
+
+    /** The distance to cover at the speed: the moving one if there is one. */
+    function distance() {
+        return global.movingDistance ? global.movingDistance : global.totalDistance;
+    }
+
     function updateEnd() {
         if (startDate && movingTime !== undefined) {
             if (startTime === undefined) {
                 startTime = '00:00:00';
             }
             let start = getDate(startDate, startTime);
-            let ratio =
-                $gpxStatistics.global.time.moving > 0
-                    ? $gpxStatistics.global.time.total / $gpxStatistics.global.time.moving
-                    : 1;
+            let ratio = timeRatio();
             let end = new Date(start.getTime() + ratio * movingTime * 1000);
             endDate = toCalendarDate(end);
             endTime = toTimeString(end);
@@ -124,10 +129,7 @@
                 endTime = '00:00:00';
             }
             let end = getDate(endDate, endTime);
-            let ratio =
-                $gpxStatistics.global.time.moving > 0
-                    ? $gpxStatistics.global.time.total / $gpxStatistics.global.time.moving
-                    : 1;
+            let ratio = timeRatio();
             let start = new Date(end.getTime() - ratio * movingTime * 1000);
             startDate = toCalendarDate(start);
             startTime = toTimeString(start);
@@ -157,11 +159,7 @@
             return;
         }
 
-        let distance =
-            $gpxStatistics.global.distance.moving > 0
-                ? $gpxStatistics.global.distance.moving
-                : $gpxStatistics.global.distance.total;
-        movingTime = (distance / speedValue) * 3600;
+        movingTime = (distance() / speedValue) * 3600;
 
         updateEnd();
     }
@@ -170,16 +168,15 @@
         if (movingTime === undefined) {
             return;
         }
-        let distance =
-            $gpxStatistics.global.distance.moving > 0
-                ? $gpxStatistics.global.distance.moving
-                : $gpxStatistics.global.distance.total;
-        setSpeed(distance / (movingTime / 3600));
+        setSpeed(distance() / (movingTime / 3600));
         updateEnd();
     }
 
+    // a single file, track or segment
     let canUpdate = $derived(
-        $selection.size === 1 && $selection.hasAnyChildren(new ListRootItem(), true, ['waypoints'])
+        ($selection.type === 'file' && $selection.fileIds.length === 1) ||
+            ($selection.type === 'track' && $selection.trackIds.length === 1) ||
+            ($selection.type === 'segment' && $selection.segmentIds.length === 1)
     );
 </script>
 
@@ -309,7 +306,7 @@
                 />
             </div>
         </div>
-        {#if $gpxStatistics.global.time.moving === 0 || $gpxStatistics.global.time.moving === undefined}
+        {#if !global.movingTime}
             <div class="mt-0.5 flex flex-row gap-1 items-center">
                 <Checkbox id="artificial-time" bind:checked={artificial} disabled={!canUpdate} />
                 <Label for="artificial-time">
@@ -324,78 +321,33 @@
             disabled={!canUpdate}
             class="grow shrink whitespace-normal h-fit min-h-8 py-1"
             onclick={() => {
-                let effectiveSpeed = getSpeed();
+                const speedValue = getSpeed();
                 if (
                     startDate === undefined ||
                     startTime === undefined ||
-                    effectiveSpeed === undefined ||
+                    speedValue === undefined ||
                     movingTime === undefined
                 ) {
                     return;
                 }
 
-                if (Math.abs(effectiveSpeed - $gpxStatistics.global.speed.moving) < 0.01) {
-                    effectiveSpeed = $gpxStatistics.global.speed.moving;
+                let effectiveSpeed: number = speedValue;
+                const movingSpeed = global.movingSpeed ?? 0;
+                if (Math.abs(effectiveSpeed - movingSpeed) < 0.01) {
+                    effectiveSpeed = movingSpeed;
                 }
 
                 let ratio = 1;
-                if (
-                    $gpxStatistics.global.speed.moving > 0 &&
-                    $gpxStatistics.global.speed.moving !== effectiveSpeed
-                ) {
-                    ratio = $gpxStatistics.global.speed.moving / effectiveSpeed;
+                if (movingSpeed > 0 && movingSpeed !== effectiveSpeed) {
+                    ratio = movingSpeed / effectiveSpeed;
                 }
 
-                let item = $selection.getSelected()[0];
-                let fileId = item.getFileId();
-                fileActionManager.applyToFile(fileId, (file) => {
-                    if (item instanceof ListFileItem) {
-                        if (artificial && !$gpxStatistics.global.time.moving) {
-                            file.createArtificialTimestamps(
-                                getDate(startDate!, startTime!),
-                                movingTime!
-                            );
-                        } else {
-                            file.changeTimestamps(
-                                getDate(startDate!, startTime!),
-                                effectiveSpeed,
-                                ratio
-                            );
-                        }
-                    } else if (item instanceof ListTrackItem) {
-                        if (artificial && !$gpxStatistics.global.time.moving) {
-                            file.createArtificialTimestamps(
-                                getDate(startDate!, startTime!),
-                                movingTime!,
-                                item.getTrackIndex()
-                            );
-                        } else {
-                            file.changeTimestamps(
-                                getDate(startDate!, startTime!),
-                                effectiveSpeed,
-                                ratio,
-                                item.getTrackIndex()
-                            );
-                        }
-                    } else if (item instanceof ListTrackSegmentItem) {
-                        if (artificial && !$gpxStatistics.global.time.moving) {
-                            file.createArtificialTimestamps(
-                                getDate(startDate!, startTime!),
-                                movingTime!,
-                                item.getTrackIndex(),
-                                item.getSegmentIndex()
-                            );
-                        } else {
-                            file.changeTimestamps(
-                                getDate(startDate!, startTime!),
-                                effectiveSpeed,
-                                ratio,
-                                item.getTrackIndex(),
-                                item.getSegmentIndex()
-                            );
-                        }
-                    }
-                });
+                const start = getDate(startDate, startTime);
+                if (artificial && !global.movingTime) {
+                    engine.createArtificialTimestamps(start, movingTime);
+                } else {
+                    engine.changeTimestamps(start, effectiveSpeed, ratio);
+                }
             }}
         >
             <CalendarClock size="16" class="shrink-0" />
diff --git a/website/src/lib/engine.ts b/website/src/lib/engine.ts
index 97bd59201..601c462af 100644
--- a/website/src/lib/engine.ts
+++ b/website/src/lib/engine.ts
@@ -672,6 +672,24 @@ class Engine {
         return this.run((w) => w.elevation(ele));
     }
 
+    /**
+     * Sets the timestamps of the selection, which starts at `startTime`: the trackpoints that
+     * have some keep their durations multiplied by `ratio`, the others follow the previous one at
+     * `speed` (km/h). Resolves to `false` when there is nothing to set, or the values are invalid.
+     */
+    changeTimestamps(startTime: Date, speed: number, ratio: number) {
+        return this.run((w) => w.changeTimestamps(startTime.getTime(), speed, ratio));
+    }
+
+    /**
+     * Makes up timestamps for the selection, which starts at `startTime` and lasts `totalTime`
+     * seconds, longer and steeper intervals taking more time. Resolves to `false` when there is
+     * nothing to set.
+     */
+    createArtificialTimestamps(startTime: Date, totalTime: number) {
+        return this.run((w) => w.createArtificialTimestamps(startTime.getTime(), totalTime));
+    }
+
     /**
      * Merges the selected files, tracks or segments into the first of them (see `MergeType`). With
      * `removeGaps`, the parts that are connected get closer in time if they have timestamps.