From a86cd9138960fc3d229d8aad3daa6d7f350e2a21 Mon Sep 17 00:00:00 2001
From: Tristan Ross <tristan.ross@midstall.com>
Date: Tue, 19 Dec 2023 23:42:47 -0800
Subject: [PATCH 1/3] os.uefi: add time to epoch conversion

---
 lib/std/os/uefi.zig | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/lib/std/os/uefi.zig b/lib/std/os/uefi.zig
index 7ad01e58e7..51702c4923 100644
--- a/lib/std/os/uefi.zig
+++ b/lib/std/os/uefi.zig
@@ -131,6 +131,30 @@ pub const Time = extern struct {
 
     /// Time is to be interpreted as local time
     pub const unspecified_timezone: i16 = 0x7ff;
+
+    fn daysInYear(year: u16, maxMonth: u4) u32 {
+        const leapYear: std.time.epoch.YearLeapKind = if (std.time.epoch.isLeapYear(year)) .leap else .not_leap;
+        var days: u32 = 0;
+        var month: u4 = 0;
+        while (month < maxMonth) : (month += 1) {
+            days += std.time.epoch.getDaysInMonth(leapYear, @enumFromInt(month + 1));
+        }
+        return days;
+    }
+
+    pub fn toEpoch(self: std.os.uefi.Time) u64 {
+        var year: u16 = 0;
+        var days: u32 = 0;
+
+        while (year < (self.year - 1971)) : (year += 1) {
+            days += daysInYear(year + 1970, 12);
+        }
+
+        days += daysInYear(self.year, @as(u4, @intCast(self.month)) - 1) + self.day;
+        const hours = self.hour + (days * 24);
+        const minutes = self.minute + (hours * 60);
+        return self.second + (minutes * 60);
+    }
 };
 
 /// Capabilities of the clock device

From 23adf095798b8345997b2cbe182c7f109fe1da49 Mon Sep 17 00:00:00 2001
From: Tristan Ross <tristan.ross@midstall.com>
Date: Tue, 19 Dec 2023 23:43:10 -0800
Subject: [PATCH 2/3] time: add uefi support

---
 lib/std/time.zig | 16 +++++++++++++++-
 1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/lib/std/time.zig b/lib/std/time.zig
index c078e97793..56927eae4c 100644
--- a/lib/std/time.zig
+++ b/lib/std/time.zig
@@ -114,6 +114,13 @@ pub fn nanoTimestamp() i128 {
         return ns;
     }
 
+    if (builtin.os.tag == .uefi) {
+        var value: std.os.uefi.Time = undefined;
+        const status = std.os.uefi.system_table.runtime_services.getTime(&value, null);
+        assert(status == .Success);
+        return @as(i128, @intCast(value.toEpoch())) * ms_per_s;
+    }
+
     var ts: os.timespec = undefined;
     os.clock_gettime(os.CLOCK.REALTIME, &ts) catch |err| switch (err) {
         error.UnsupportedClock, error.Unexpected => return 0, // "Precision of timing depends on hardware and OS".
@@ -176,7 +183,7 @@ pub const Instant = struct {
     // true if we should use clock_gettime()
     const is_posix = switch (builtin.os.tag) {
         .wasi => builtin.link_libc,
-        .windows => false,
+        .windows, .uefi => false,
         else => true,
     };
 
@@ -197,6 +204,13 @@ pub const Instant = struct {
             return Instant{ .timestamp = ns };
         }
 
+        if (builtin.os.tag == .uefi) {
+            var value: std.os.uefi.Time = undefined;
+            const status = std.os.uefi.system_table.runtime_services.getTime(&value, null);
+            if (status != .Success) return error.Unsupported;
+            return Instant{ .timestamp = value.toEpoch() };
+        }
+
         // On darwin, use UPTIME_RAW instead of MONOTONIC as it ticks while suspended.
         // On linux, use BOOTTIME instead of MONOTONIC as it ticks while suspended.
         // On freebsd derivatives, use MONOTONIC_FAST as currently there's no precision tradeoff.

From 97fd100471ea74acd3a18c5bbc95efc8f8978b93 Mon Sep 17 00:00:00 2001
From: Tristan Ross <tristan.ross@midstall.com>
Date: Wed, 20 Dec 2023 09:33:59 -0800
Subject: [PATCH 3/3] os.uefi: add ns to epoch

---
 lib/std/os/uefi.zig | 3 ++-
 lib/std/time.zig    | 2 +-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/std/os/uefi.zig b/lib/std/os/uefi.zig
index 51702c4923..165c3df249 100644
--- a/lib/std/os/uefi.zig
+++ b/lib/std/os/uefi.zig
@@ -153,7 +153,8 @@ pub const Time = extern struct {
         days += daysInYear(self.year, @as(u4, @intCast(self.month)) - 1) + self.day;
         const hours = self.hour + (days * 24);
         const minutes = self.minute + (hours * 60);
-        return self.second + (minutes * 60);
+        const seconds = self.second + (minutes * std.time.s_per_min);
+        return self.nanosecond + (seconds * std.time.ns_per_s);
     }
 };
 
diff --git a/lib/std/time.zig b/lib/std/time.zig
index 56927eae4c..dad81385e9 100644
--- a/lib/std/time.zig
+++ b/lib/std/time.zig
@@ -118,7 +118,7 @@ pub fn nanoTimestamp() i128 {
         var value: std.os.uefi.Time = undefined;
         const status = std.os.uefi.system_table.runtime_services.getTime(&value, null);
         assert(status == .Success);
-        return @as(i128, @intCast(value.toEpoch())) * ms_per_s;
+        return value.toEpoch();
     }
 
     var ts: os.timespec = undefined;