diff --git a/src/header/sys_time/mod.rs b/src/header/sys_time/mod.rs
index af5e895d03..31ae5bb0b2 100644
--- a/src/header/sys_time/mod.rs
+++ b/src/header/sys_time/mod.rs
@@ -1,4 +1,6 @@
-//! sys/time implementation for Redox, following http://pubs.opengroup.org/onlinepubs/7908799/xsh/systime.h.html
+//! `sys/time.h` implementation.
+//!
+//! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_time.h.html>.
 
 use crate::{
     c_str::CStr,
@@ -8,16 +10,41 @@ use crate::{
 };
 use core::ptr::null;
 
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_time.h.html>.
+///
+/// # Deprecation
+/// The `ITIMER_REAL` symbolic constant was marked obsolescent in the Open
+/// Group Base Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 pub const ITIMER_REAL: c_int = 0;
+
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_time.h.html>.
+///
+/// # Deprecation
+/// The `ITIMER_VIRTUAL` symbolic constant was marked obsolescent in the Open
+/// Group Base Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 pub const ITIMER_VIRTUAL: c_int = 1;
+
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_time.h.html>.
+///
+/// # Deprecation
+/// The `ITIMER_PROF` symbolic constant was marked obsolescent in the Open
+/// Group Base Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 pub const ITIMER_PROF: c_int = 2;
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_time.h.html>.
+///
+/// TODO: specified for `sys/select.h` in modern POSIX?
 #[repr(C)]
 #[derive(Default)]
 pub struct timeval {
     pub tv_sec: time_t,
     pub tv_usec: suseconds_t,
 }
+
+/// Non-POSIX, see <https://www.man7.org/linux/man-pages/man2/gettimeofday.2.html>.
 #[repr(C)]
 #[derive(Default)]
 pub struct timezone {
@@ -25,6 +52,12 @@ pub struct timezone {
     pub tz_dsttime: c_int,
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_time.h.html>.
+///
+/// # Deprecation
+/// The `itimerval` struct was marked obsolescent in the Open Group Base
+/// Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 #[repr(C)]
 #[derive(Default)]
 pub struct itimerval {
@@ -32,11 +65,20 @@ pub struct itimerval {
     pub it_value: timeval,
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sys_time.h.html>.
+///
+/// TODO: specified for `sys/select.h` in modern POSIX?
 #[repr(C)]
 pub struct fd_set {
     pub fds_bits: [c_long; 16usize],
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/functions/getitimer.html>.
+///
+/// # Deprecation
+/// The `getitimer()` function was marked obsolescent in the Open Group Base
+/// Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 #[no_mangle]
 pub unsafe extern "C" fn getitimer(which: c_int, value: *mut itimerval) -> c_int {
     Sys::getitimer(which, value)
@@ -44,6 +86,12 @@ pub unsafe extern "C" fn getitimer(which: c_int, value: *mut itimerval) -> c_int
         .or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/functions/getitimer.html>.
+///
+/// # Deprecation
+/// The `setitimer()` function was marked obsolescent in the Open Group Base
+/// Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 #[no_mangle]
 pub unsafe extern "C" fn setitimer(
     which: c_int,
@@ -55,11 +103,25 @@ pub unsafe extern "C" fn setitimer(
         .or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9699919799/functions/gettimeofday.html>.
+///
+/// See also <https://www.man7.org/linux/man-pages/man2/gettimeofday.2.html>
+/// for further details on the `tzp` argument.
+///
+/// # Deprecation
+/// The `gettimeofday()` function was marked obsolescent in the Open Group Base
+/// Specifications Issue 7, and removed in Issue 8.
+#[deprecated]
 #[no_mangle]
 pub unsafe extern "C" fn gettimeofday(tp: *mut timeval, tzp: *mut timezone) -> c_int {
     Sys::gettimeofday(tp, tzp).map(|()| 0).or_minus_one_errno()
 }
 
+/// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/utimes.html>.
+///
+/// # Deprecation
+/// The `utimes()` function was marked legacy in the Open Group Base
+/// Specifications Issue 6, and then unmarked in Issue 7.
 #[no_mangle]
 pub unsafe extern "C" fn utimes(path: *const c_char, times: *const timeval) -> c_int {
     let path = CStr::from_ptr(path);