diff --git a/std/os/time.zig b/std/os/time.zig
index 99c8b5992..abb641284 100644
--- a/std/os/time.zig
+++ b/std/os/time.zig
@@ -13,44 +13,35 @@ const posix = std.os.posix;
 
 pub const epoch = @import("epoch.zig");
 
-/// Sleep for the specified duration
+/// Spurious wakeups are possible and no precision of timing is guaranteed.
 pub fn sleep(nanoseconds: u64) void {
     switch (builtin.os) {
         Os.linux, Os.macosx, Os.ios, Os.freebsd, Os.netbsd => {
             const s = nanoseconds / ns_per_s;
             const ns = nanoseconds % ns_per_s;
-            posixSleep(@intCast(u63, s), @intCast(u63, ns));
+            posixSleep(s, ns);
         },
         Os.windows => {
             const ns_per_ms = ns_per_s / ms_per_s;
             const milliseconds = nanoseconds / ns_per_ms;
-            windows.Sleep(@intCast(windows.DWORD, milliseconds));
+            const ms_that_will_fit = std.math.cast(windows.DWORD, milliseconds) catch std.math.maxInt(windows.DWORD);
+            windows.Sleep(ms_that_will_fit);
         },
         else => @compileError("Unsupported OS"),
     }
 }
 
-pub fn posixSleep(seconds: u63, nanoseconds: u63) void {
-    var req: posix.timespec = undefined;
+/// Spurious wakeups are possible and no precision of timing is guaranteed.
+pub fn posixSleep(seconds: u64, nanoseconds: u64) void {
+    var req = posix.timespec{
+        .tv_sec = std.math.cast(isize, seconds) catch std.math.maxInt(isize),
+        .tv_nsec = std.math.cast(isize, nanoseconds) catch std.math.maxInt(isize),
+    };
     var rem: posix.timespec = undefined;
-
-    var req_sec = seconds;
-    var req_nsec = nanoseconds;
-
     while (true) {
-        req.tv_sec = math.min(math.maxInt(isize), req_sec);
-        req.tv_nsec = @intCast(isize, req_nsec);
-
-        req_sec -= @intCast(u63, req.tv_sec);
-        req_nsec = 0;
-
         const ret_val = posix.nanosleep(&req, &rem);
         const err = posix.getErrno(ret_val);
         switch (err) {
-            0 => {
-                // If there's still time to wait keep running the loop
-                if (req_sec == 0 and req_nsec == 0) return;
-            },
             posix.EFAULT => unreachable,
             posix.EINVAL => {
                 // Sometimes Darwin returns EINVAL for no reason.
@@ -58,10 +49,10 @@ pub fn posixSleep(seconds: u63, nanoseconds: u63) void {
                 return;
             },
             posix.EINTR => {
-                req_sec += @intCast(u63, rem.tv_sec);
-                req_nsec = @intCast(u63, rem.tv_nsec);
+                req = rem;
                 continue;
             },
+            // This prong handles success as well as unexpected errors.
             else => return,
         }
     }