PNG, PDF, EPS, legacy `.ai`, packaged zips and saved `.vectorcraft` files
record the wall-clock time they were made in, so the same commands run twice
gave different bytes although the pixels matched (#2880):
PDF /CreationDate and /ModDate D:20261018155816 vs D:20261018155817
PNG the `Creation Time` tEXt entry
.vectorcraft one byte of the stored date
SVG carries no time, and already repeated
`metadata::output_time` is the time a file records: `SOURCE_DATE_EPOCH` when it
holds a non-negative whole number of seconds, else the clock, as the
reproducible-builds specification defines it. A date a command is given
(`file.new {created}`, a save's `modified`) still wins over the variable, and a
blank, negative or non-numeric value is ignored so that an export is never
refused over the environment.
`metadata::now_unix` keeps the real clock and now has exactly two callers, both
of which must not be pinnable from the environment: the recovery heartbeat, and
the seed PDF encryption draws on.
- Format v3: optional gzip (Preferences > File Handling > Use Compression, or
document.save {compress}); compressed files open by their magic bytes, legacy
ones too.
- Every file write goes to a temporary file renamed over the target (engine
writes and the desktop app's writer), so a failed save keeps the old file.
- Only the images the document uses are written.
- Document keys from newer versions are kept (Document.extra, flattened).
- Assigned colour profiles are a real field (Document.color_profiles),
migrated from unknown.colorProfiles on load.
- document.save {version: 1|2} writes files older versions open; {preview}
embeds a PNG of the first artboard of at most 256 px.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Hamza