--- title: "Change a video’s recorded date in C#" url: https://recursiveai.org/onemedia/cookbook/change-video-recorded-date/ description: "Change the recorded date (creation time) of an MP4 or MOV video in C# with OneMedia: set every date field the file carries in its own format and zone, get a report of what was written and left, and read it back with ExifTool and ffprobe. A preview." version: "0.6.0-preview.1" --- # Change a video’s recorded date in C# `Media.SetCaptureTime(input, output, when)` sets the time a recording was made in every date field the file carries, each in that field’s own notation and zone, and returns a report of what it wrote, what it left and which dates still disagree. The audio and video bytes are copied unchanged. A preview in 0.6.0-preview.1. The inputs are MDN’s CC0 flower clip and the iPhone-style test file from the OneMedia repository (MIT OR Apache-2.0; synthetic picture, invented tags). ```shell dotnet new console -o Redate && cd Redate dotnet add package RecursiveAI.OneMedia --version 0.6.0-preview.1 curl -L -o flower.mp4 https://interactive-examples.mdn.mozilla.net/media/cc0-videos/flower.mp4 curl -L -o iphone-style.mov https://raw.githubusercontent.com/recursive-ai-oss/onemedia-csharp/v0.6.0-preview.1/testdata/metadata/tags_keys.mov ``` Put this in `Program.cs` and run `dotnet run`: ```csharp using RecursiveAI.OneMedia; using RecursiveAI.OneMedia.Tags; // 00:30 on 1 May 2024 in a UTC+2 zone, which is 22:30 UTC on 30 April. var when = new DateTimeOffset(2024, 5, 1, 0, 30, 0, TimeSpan.FromHours(2)); foreach ((string input, string output) in new[] { ("flower.mp4", "flower-redated.mp4"), ("iphone-style.mov", "iphone-redated.mov") }) { using (MediaFile before = Media.Open(input)) Console.WriteLine($"{input}: recorded {before.CaptureTime}"); // Writes a new file; the input is not touched. CaptureTimeReport report = Media.SetCaptureTime(input, output, when); Console.WriteLine($" header times written as {(report.HeaderTimesLocal ? "local" : "UTC")} ({report.HeaderTimesBasis})"); foreach (DateFieldWrite w in report.Written) Console.WriteLine($" wrote {w.System}:{w.Field}: {w.OldValue ?? "(none)"} -> {w.NewValue}"); foreach (DateFieldLeft left in report.Left) Console.WriteLine($" left {left.System}:{left.Field}: {left.Reason}"); foreach (DateDisagreement d in report.Disagreements) Console.WriteLine($" still differs: {d.Source} = {d.RawValue} ({d.Note})"); using (MediaFile after = Media.Open(output)) Console.WriteLine($"{output}: recorded {after.CaptureTime}"); } ``` ```text flower.mp4: recorded 2018-03-07T15:21:21Z header times written as UTC (specification: header times are UTC) wrote mvhd:creation_time: 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote mvhd:modification_time: 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote tkhd:creation_time (track 1): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote tkhd:modification_time (track 1): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote mdhd:creation_time (track 1): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote mdhd:modification_time (track 1): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote tkhd:creation_time (track 2): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote tkhd:modification_time (track 2): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote mdhd:creation_time (track 2): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 wrote mdhd:modification_time (track 2): 2018-03-07T15:21:21 -> 2024-04-30T22:30:00 flower-redated.mp4: recorded 2024-04-30T22:30:00Z iphone-style.mov: recorded 2023-04-05T10:11:12+02:00 header times written as UTC (specification: header times are UTC) wrote mvhd:creation_time: 1904-01-01T00:00:00 -> 2024-04-30T22:30:00 wrote mvhd:modification_time: 1904-01-01T00:00:00 -> 2024-04-30T22:30:00 wrote mdta:com.apple.quicktime.creationdate: 2023-04-05T10:11:12+0200 -> 2024-05-01T00:30:00+0200 left tkhd:creation_time (track 1): unset (0); left unset left mdhd:creation_time (track 1): unset (0); left unset left tkhd:creation_time (track 2): unset (0); left unset left mdhd:creation_time (track 2): unset (0); left unset iphone-redated.mov: recorded 2024-05-01T00:30:00+02:00 ``` - **The movie and track headers** (`mvhd`, `tkhd`, `mdhd`) hold UTC seconds, as the MP4 specification says, so 00:30 at UTC+2 is written as 22:30 on 30 April. A device that stores local time there can be matched with `CaptureTimeOptions.HeaderTimesAreLocal` or a device profile; the report says which rule it used. - **Apple’s `creationdate` key** keeps the offset, `+0200`, as Apple cameras write it. It ranks first when OneMedia reads the date back, so the iPhone-style file reads back with its zone, and the flower clip, which has only header times, reads back in UTC. - **Header times that were never set.** Every header time in the iPhone-style file was 0. Its track headers are left and listed with the reason; its movie header was written, as the report says. That is the documented behavior: the [date-writes page](https://recursiveai.org/onemedia/docs/date-writes/) says “`mvhd` is always written, even when both its times are 0, because it is the date Explorer, Photos and AVFoundation show; a `tkhd` or `mdhd` whose times are both 0 is left unset and listed under Left”. Fields that are absent are not added in MP4 and MOV: no `©day` or XMP is created. ## Read it back with ExifTool and ffprobe ```shell exiftool -a -G1 -time:all --File:all flower-redated.mp4 iphone-redated.mov ``` ```text ======== flower-redated.mp4 [QuickTime] Create Date : 2024:04:30 22:30:00 [QuickTime] Modify Date : 2024:04:30 22:30:00 [Track1] Track Create Date : 2024:04:30 22:30:00 [Track1] Track Modify Date : 2024:04:30 22:30:00 [Track1] Media Create Date : 2024:04:30 22:30:00 [Track1] Media Modify Date : 2024:04:30 22:30:00 [Track2] Track Create Date : 2024:04:30 22:30:00 [Track2] Track Modify Date : 2024:04:30 22:30:00 [Track2] Media Create Date : 2024:04:30 22:30:00 [Track2] Media Modify Date : 2024:04:30 22:30:00 ======== iphone-redated.mov [QuickTime] Create Date : 2024:04:30 22:30:00 [QuickTime] Modify Date : 2024:04:30 22:30:00 [Track1] Track Create Date : 0000:00:00 00:00:00 [Track1] Track Modify Date : 0000:00:00 00:00:00 [Track1] Media Create Date : 0000:00:00 00:00:00 [Track1] Media Modify Date : 0000:00:00 00:00:00 [Track2] Track Create Date : 0000:00:00 00:00:00 [Track2] Track Modify Date : 0000:00:00 00:00:00 [Track2] Media Create Date : 0000:00:00 00:00:00 [Track2] Media Modify Date : 0000:00:00 00:00:00 [Keys] Creation Date : 2024:05:01 00:30:00+02:00 2 image files read ``` ```shell for f in flower-redated.mp4 iphone-redated.mov; do echo "$f" ffprobe -v error -show_entries format_tags=creation_time,com.apple.quicktime.creationdate:stream_tags=creation_time -of default=nw=1 $f done ``` ```text flower-redated.mp4 TAG:creation_time=2024-04-30T22:30:00.000000Z TAG:creation_time=2024-04-30T22:30:00.000000Z TAG:creation_time=2024-04-30T22:30:00.000000Z iphone-redated.mov TAG:creation_time=2024-04-30T22:30:00.000000Z TAG:com.apple.quicktime.creationdate=2024-05-01T00:30:00+0200 ``` ExifTool shows the header times in UTC and the Apple key with its offset; ffprobe reads the headers as `creation_time` in UTC and the key as written. It lists `creation_time` for the file and for each track whose header holds one, so the flower clip shows three and the iPhone-style file one. ## What file managers and photo apps show From the README: written dates were “Read back in ExifTool 13.60, MediaInfo 26.10 and ffprobe 7.0.2. **Windows Explorer and Photos (Windows 11) and macOS AVFoundation were checked:** they show the `mvhd` date, not `©day` or Apple’s `creationdate`. **Apple Photos and Google Photos display checks are pending** (they need a GUI session and an account)”. Those display checks were run by the OneMedia project, not by us for this page; the table is on its [date-writes page](https://recursiveai.org/onemedia/docs/date-writes/). The practical upshot: Windows and macOS show the `mvhd` time, read as UTC and displayed in the viewer’s own zone. ## From the command line `onemedia tags clip.mp4 --capture-time 2024-05-01T00:30:00+02:00 --out redated.mp4` does the same and prints the report; `--replace` or `--in-place` writes to the file itself. ## Limits - **A preview.** The README: “Checked against ExifTool 13.60 and MediaInfo 26.10 on published samples and on files we generate, not on a corpus of device recordings.” Its device-profile caveat applies to the local-time rule: “Device-profile rows for phones and cameras rest on ExifTool’s tag documentation and the few vendor samples available; treat the zone rules for devices not listed there as unverified”. - **Formats.** MP4, MOV and 3GP; Matroska and WebM (`DateUTC`, `DATE_RECORDED`); WAV/BWF/RF64; MP3; FLAC, Ogg Vorbis and Opus; ASF. Not AVI, MPEG-TS, PS, FLV, DV, CAF or AIFF. - **Not rewritten:** GPS times in telemetry tracks (the report lists them as disagreements when they differ), `tmcd` timecode, sidecar files, and the file system’s own dates. - **Range.** 1904 to 2262; a version 0 header box holds dates to 2040 and is left, with a note, for a later date. - **Saving.** `Media.SetCaptureTime` writes a new file; `CaptureTimeWriter.Save` replaces the file through a temporary file and `SaveInPlace` writes within existing padding only. To change other tags, see [Edit MP4, MKV and MP3 tags](https://recursiveai.org/onemedia/cookbook/edit-video-tags/).