std.Io: Standardize the epoch as 1970-01-01T00:00:00Z

lib/std/Io.zig

@@ -734,16 +734,16 @@ pub const Clock = enum {
     /// A settable system-wide clock that measures real (i.e. wall-clock)
     /// time. This clock is affected by discontinuous jumps in the system
     /// time (e.g., if the system administrator manually changes the
-    /// clock), and by frequency adjust‐ ments performed by NTP and similar
+    /// clock), and by frequency adjustments performed by NTP and similar
     /// applications.
     ///
     /// This clock normally counts the number of seconds since 1970-01-01
     /// 00:00:00 Coordinated Universal Time (UTC) except that it ignores
     /// leap seconds; near a leap second it is typically adjusted by NTP to
     /// stay roughly in sync with UTC.
     ///
-    /// The epoch is implementation-defined. For example NTFS/Windows uses
-    /// 1601-01-01.
+    /// The epoch is 1970-01-01T00:00:00Z, which corresponds to a clock
+    /// value of zero.
     real,
     /// A nonsettable system-wide clock that represents time since some
     /// unspecified point in the past.

lib/std/Io/Threaded.zig

@@ -2864,7 +2864,8 @@ fn nowWindows(userdata: ?*anyopaque, clock: Io.Clock) Io.Clock.Error!Io.Timestam
         .real => {
             // RtlGetSystemTimePrecise() has a granularity of 100 nanoseconds
             // and uses the NTFS/Windows epoch, which is 1601-01-01.
-            return .{ .nanoseconds = @as(i96, windows.ntdll.RtlGetSystemTimePrecise()) * 100 };
+            const epoch_100_ns = std.time.epoch.windows * (std.time.ns_per_s / 100);
+            return .{ .nanoseconds = @as(i96, windows.ntdll.RtlGetSystemTimePrecise() + epoch_100_ns) * 100 };
         },
         .awake, .boot => {
             // QPC on windows doesn't fail on >= XP/2000 and includes time suspended.