help/dates: rephrase explanation of internal format

The old explanation referred to the two numbers as "unixtime" and
"offset" without really defining those terms.

mercurial/help/dates.txt

@@ -1,36 +1,36 b''
 Some commands allow the user to specify a date, e.g.:
 
 - backout, commit, import, tag: Specify the commit date.
 - log, revert, update: Select revision(s) by date.
 
 Many date formats are valid. Here are some examples:
 
 - ``Wed Dec 6 13:18:29 2006`` (local timezone assumed)
 - ``Dec 6 13:18 -0600`` (year assumed, time offset provided)
 - ``Dec 6 13:18 UTC`` (UTC and GMT are aliases for +0000)
 - ``Dec 6`` (midnight)
 - ``13:18`` (today assumed)
 - ``3:39`` (3:39AM assumed)
 - ``3:39pm`` (15:39)
 - ``2006-12-06 13:18:29`` (ISO 8601 format)
 - ``2006-12-6 13:18``
 - ``2006-12-6``
 - ``12-6``
 - ``12/6``
 - ``12/6/6`` (Dec 6 2006)
 
 Lastly, there is Mercurial's internal format:
 
 - ``1165432709 0`` (Wed Dec 6 13:18:29 2006 UTC)
 
-This is the internal representation format for dates. unixtime is the
-number of seconds since the epoch (1970-01-01 00:00 UTC). offset is
-the offset of the local timezone, in seconds west of UTC (negative if
-the timezone is east of UTC).
+This is the internal representation format for dates. The first number
+is the number of seconds since the epoch (1970-01-01 00:00 UTC). The
+second is the offset of the local timezone, in seconds west of UTC
+(negative if the timezone is east of UTC).
 
 The log command also accepts date ranges:
 
 - ``<{datetime}`` - at or before a given date/time
 - ``>{datetime}`` - on or after a given date/time
 - ``{datetime} to {datetime}`` - a date range, inclusive
 - ``-{days}`` - within a given number of days of today