defaultVideosToUTC/backfillTimezones improvements

- if backfillTimezones=false, no timezone defaults are used unless the file is a video and defaultVideosToUTC=true
- backfillTimezones now defaults to true
- use new ExifDateTime.inferredZone to determine when to backfill zones
- avoid File stat tags (which use SystemZone) as a candidate EDT for zone adoption
- if defaultVideosToUTC=true, Tags.tz isn't forced to UTC anymore if we can extract a reasonable zone, but we still parse all datestamps with a UTC default backstop

CHANGELOG.md

@@ -26,6 +26,30 @@ vendored versions of ExifTool match the version that they vendor.
 
 ## Version history
 
+### v23.0.0
+
+- 🏚️ Dropped support for Node.js v16, which is [End-of-Life](https://nodejs.org/en/blog/announcements/nodejs16-eol).
+
+- 💔/🐞 If `defaultVideosToUTC` is set to `true`, `read()` will now allow non-UTC
+  timezones extractable from other tags to be assigned to `.tz`. Prior
+  versions would simply force `.tz` to "UTC" for all videos, which wasn't
+  great. Note that "UTC" is still used as the default timezone for all
+  datestamps without explicit timezones, just as prior versions did. See [issue
+  #156](https://github.com/photostructure/exiftool-vendored.js/issues/156) for
+  details.
+
+- 💔 `backfillTimezones` now defaults to `true`. Although this is likely to be
+  what people expect, know that there are edge and corner cases that you
+  should be aware of.
+
+- 💔 If `backfillTimezones` is set to `false`, `ExifDateTime` will no longer
+  use the current file's `.tz` as a default. Prior versions would inherit the
+  file's `.tz`, which might be incorrect.
+
+- 📦 `ExifDateTime` now includes an `.inferredZone` field, which may be useful
+  in helping to determine how "trustworthy" the zone and actual datestamp
+  value is.
+
 ### v22.2.3
 
 - 🐞 Apply the v22.2.3 bugfix _even wider_ (just found a `SubSecTime` value of "01" in the wild, and it was happily parsed into today's date, oops).

src/DefaultExifToolOptions.ts

@@ -48,7 +48,7 @@ export const DefaultExifToolOptions: Omit<
   includeImageDataMD5: undefined,
   imageHashType: false,
   defaultVideosToUTC: true,
-  backfillTimezones: false, // to retain prior behavior
+  backfillTimezones: true,
   inferTimezoneFromDatestamps: false, // to retain prior behavior
   geoTz: geoTz,
   isIgnorableError: isIgnorableWarning,

src/ExifToolOptions.ts

@@ -128,7 +128,13 @@ export interface ExifToolOptions
    * If set to `true`, and `defaultVideosToUTC` is also `true`, we'll try
    * backfilling timezones for date-times that are UTC, as well.
    *
-   * This defaults to false to retain prior versions' behavior.
+   * Setting this to `false` removes **all** timezone inference--only those
+   * date-times with an explicit offset will have a defined timezone. Prior
+   * versions of exiftool-vendored would use the file's `.tz` as a backstop
+   * even if this was set to `false`.
+   *
+   * As of version 23, this now defaults to `true`, as it's more likely to be
+   * what people expect.
    */
   backfillTimezones: boolean
 
@@ -140,7 +146,8 @@ export interface ExifToolOptions
    * datestamp whose tag starts with "Creat" and includes an offset? (This
    * means CreateDateSubSec, CreateDate, and CreationDate will be considered).
    *
-   * This defaults to false to retain prior versions' behavior.
+   * This defaults to false as it both retains prior behavior and means fewer
+   * "fuzzy" heuristics are enabled by default.
    */
   inferTimezoneFromDatestamps: boolean