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+'\" t
+.\" Copyright 1993 David Metcalfe (david@prism.demon.co.uk)
+.\"
+.\" SPDX-License-Identifier: Linux-man-pages-copyleft
+.\"
+.\" References consulted:
+.\"     Linux libc source code
+.\"     Lewine's _POSIX Programmer's Guide_ (O'Reilly & Associates, 1991)
+.\"     386BSD man pages
+.\" Modified Sat Jul 24 19:48:17 1993 by Rik Faith (faith@cs.unc.edu)
+.TH difftime 3 2023-07-20 "Linux man-pages 6.05.01"
+.SH NAME
+difftime \- calculate time difference
+.SH LIBRARY
+Standard C library
+.RI ( libc ", " \-lc )
+.SH SYNOPSIS
+.nf
+.B #include <time.h>
+.PP
+.BI "double difftime(time_t " time1 ", time_t " time0 );
+.fi
+.SH DESCRIPTION
+The
+.BR difftime ()
+function returns the number of seconds elapsed
+between time \fItime1\fP and time \fItime0\fP, represented as a
+.IR double .
+Each of the times is specified in calendar time, which means its
+value is a measurement (in seconds) relative to the
+Epoch, 1970-01-01 00:00:00 +0000 (UTC).
+.SH ATTRIBUTES
+For an explanation of the terms used in this section, see
+.BR attributes (7).
+.TS
+allbox;
+lbx lb lb
+l l l.
+Interface	Attribute	Value
+T{
+.na
+.nh
+.BR difftime ()
+T}	Thread safety	MT-Safe
+.TE
+.sp 1
+.SH STANDARDS
+C11, POSIX.1-2008.
+.SH HISTORY
+POSIX.1-2001, C89, SVr4, 4.3BSD.
+.SH NOTES
+On a POSIX system,
+.I time_t
+is an arithmetic type, and one could just
+define
+.PP
+.in +4n
+.EX
+#define my_difftime(t1,t0) (double)(t1 \- t0)
+.EE
+.in
+.PP
+when the possible overflow in the subtraction is not a concern.
+.SH SEE ALSO
+.BR date (1),
+.BR gettimeofday (2),
+.BR time (2),
+.BR ctime (3),
+.BR gmtime (3),
+.BR localtime (3)