From 7fcd2b8c9925cc95b4dcb94c170bd42bc6b0d5bf Mon Sep 17 00:00:00 2001
From: NetterSilver <133535268+Silvertree2010@users.noreply.github.com>
Date: Thu, 22 Oct 2026 17:32:10 +0000
Subject: [PATCH] Write capture time UTC offset and sub-seconds in write_exif

Found while testing crates/meta/src/exif.rs:462 (write_exif; compare the reader in from_tiff at crates/meta/src/exif.rs:96-107)

Co-Authored-By: Claude Haiku 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
---
 crates/meta/src/exif.rs | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/crates/meta/src/exif.rs b/crates/meta/src/exif.rs
index cb45274d1..ab2691c30 100644
--- a/crates/meta/src/exif.rs
+++ b/crates/meta/src/exif.rs
@@ -496,6 +496,19 @@ pub fn write_exif(meta: &Metadata) -> Vec<u8> {
             ex.set(tag, v);
         }
     }
+    if let Some(d) = meta.capture_time {
+        let offset = d.offset_minutes.map(|o| {
+            let sign = if o < 0 { '-' } else { '+' };
+            format!("{sign}{:02}:{:02}", o.abs() / 60, o.abs() % 60)
+        });
+        let subsec = (d.millis != 0).then(|| format!("{:03}", d.millis));
+        for (tag, v) in [(t::OFFSET_TIME, &offset), (t::OFFSET_TIME_ORIGINAL, &offset), (t::SUBSEC_TIME, &subsec), (t::SUBSEC_TIME_ORIGINAL, &subsec)]
+        {
+            if let Some(v) = v {
+                ex.set(tag, Value::Ascii(v.clone()));
+            }
+        }
+    }
     ifd0.set_child(t::EXIF_IFD, ex);
     if let Some(g) = meta.gps {
         let dms = |v: f64| {
@@ -524,6 +537,14 @@ pub fn write_exif(meta: &Metadata) -> Vec<u8> {
 mod write_tests {
     use super::*;
 
+    #[test]
+    fn capture_time_offset_and_subsec_round_trip() {
+        for iso in ["2026-09-20T05:40:00.250+02:00", "2026-09-20T05:40:00.005-03:30", "2026-09-20T05:40:00"] {
+            let m = Metadata { capture_time: DateTime::parse_iso(iso), ..Default::default() };
+            assert_eq!(read_exif(&write_exif(&m)).capture_time, m.capture_time, "{iso}");
+        }
+    }
+
     #[test]
     fn exif_round_trips() {
         let m = Metadata {