From 68a21aeaf8c1d17298efd2655c5ac0805930ec76 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Thu, 23 Apr 2026 23:29:37 +0300
Subject: [PATCH] time: fix `time.Time{}` value is wrong? (fixes #25346)

---
 vlib/time/time.c.v                 | 29 ++++++++++++++++++++---------
 vlib/time/time_test.v              | 14 +++++++++++++-
 vlib/time/utc_vs_local_time_test.v |  2 +-
 3 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/vlib/time/time.c.v b/vlib/time/time.c.v
index afb8e7cfb..c9c769fef 100644
--- a/vlib/time/time.c.v
+++ b/vlib/time/time.c.v
@@ -60,21 +60,32 @@ fn time_with_unix(t Time) Time {
 	if t.unix != 0 {
 		return t
 	}
-	tt := C.tm{
-		tm_sec:  t.second
-		tm_min:  t.minute
-		tm_hour: t.hour
-		tm_mday: t.day
-		tm_mon:  t.month - 1
-		tm_year: t.year - 1900
+	normalized := normalize_zero_date_parts(t)
+	return Time{
+		...normalized
+		unix: time_fields_to_unix(normalized)
+	}
+}
+
+@[inline]
+fn normalize_zero_date_parts(t Time) Time {
+	if t.month != 0 && t.day != 0 {
+		return t
 	}
-	utime := make_unix_time(tt)
 	return Time{
 		...t
-		unix: utime
+		month: if t.month == 0 { 1 } else { t.month }
+		day:   if t.day == 0 { 1 } else { t.day }
 	}
 }
 
+@[inline]
+fn time_fields_to_unix(t Time) i64 {
+	return i64(t.days_from_unix_epoch()) * i64(seconds_per_day) +
+		i64(t.hour) * i64(seconds_per_hour) + i64(t.minute) * i64(seconds_per_minute) +
+		i64(t.second)
+}
+
 // ticks returns the number of milliseconds since the UNIX epoch.
 // On Windows ticks returns the number of milliseconds elapsed since system start.
 pub fn ticks() i64 {
diff --git a/vlib/time/time_test.v b/vlib/time/time_test.v
index 9ffd8409f..44f7e4abd 100644
--- a/vlib/time/time_test.v
+++ b/vlib/time/time_test.v
@@ -502,6 +502,18 @@ fn test_parse_weekday() {
 
 fn test_empty_time() {
 	t := time.Time{}
-	// assert t.unix() == -62169984000
+	assert t.unix() == -62167132800
+	assert t.format_rfc3339() == '0000-01-01T00:00:00.000Z'
+	assert t == time.parse_rfc3339(t.format_rfc3339())!
 	assert t.custom_format('MMMM YYYY') == 'January 0'
 }
+
+fn test_pre_epoch_unix_calculation() {
+	assert time.new(time.Time{}).unix() == -62167132800
+	assert time.new(
+		year:  1
+		month: 1
+		day:   1
+	).unix() == -62135596800
+	assert time.parse_rfc3339('0001-01-01T00:00:00Z')!.unix() == -62135596800
+}
diff --git a/vlib/time/utc_vs_local_time_test.v b/vlib/time/utc_vs_local_time_test.v
index 685664ab6..a0fd10be7 100644
--- a/vlib/time/utc_vs_local_time_test.v
+++ b/vlib/time/utc_vs_local_time_test.v
@@ -44,5 +44,5 @@ fn test_utc_to_local() {
 	}
 	sz := z.format_rfc3339()
 	dump(sz)
-	assert sz == '0000-00-00T00:00:00.000Z'
+	assert sz == '0000-01-01T00:00:00.000Z'
 }
-- 
2.39.5