+@node Seconds since the Epoch
+@section Seconds since the Epoch
+
+If you precede a number with @samp{@@}, it represents an internal time
+stamp as a count of seconds. The number can contain an internal
+decimal point (either @samp{.} or @samp{,}); any excess precision not
+supported by the internal representation is truncated toward minus
+infinity.
+
+@cindex beginning of time, for @acronym{POSIX}
+@cindex epoch, for @acronym{POSIX}
+Internally, computer times are represented as a count of seconds since
+an epoch---a well-defined point of time. On @acronym{GNU} and
+@acronym{POSIX} systems, the epoch is 1970-01-01 00:00:00 @sc{utc}, so
+@samp{@@0} represents this time, @samp{@@1} represents 1970-01-01
+00:00:01 @sc{utc}, and so forth. @acronym{GNU} and most other
+@acronym{POSIX}-compliant systems support such times as an extension
+to @acronym{POSIX}, using negative counts, so that @samp{@@-1}
+represents 1969-12-31 23:59:59 @sc{utc}.
+
+Traditional Unix systems count seconds with 32-bit two's-complement
+integers and can represent times from 1901-12-13 20:45:52 through
+2038-01-19 03:14:07 @sc{utc}. More modern systems use 64-bit counts
+of seconds with nanosecond subcounts, and can represent all the times
+in the known lifetime of the universe to a resolution of 1 nanosecond.
+
+On most systems, these counts ignore the presence of leap seconds.
+For example, on most systems @samp{@@915148799} represents 1998-12-31
+23:59:59 @sc{utc}, @samp{@@915148800} represents 1999-01-01 00:00:00
+@sc{utc}, and there is no way to represent the intervening leap second
+1998-12-31 23:59:60 @sc{utc}.