There are some cases when future dates display as less than a minute ago, which is really annoying for mods.
And also may affect phpbb on end of ban/poll dates.

Testing cases:
Set your date-format to something with || so it's shortened
than put something like:

echo $user->format_date(time() - 30) . '<br />';

echo $user->format_date(time()) . '<br />';

echo $user->format_date(time() + 3600) . '<br />';

echo $user->format_date(time() + 7200) . '<br />';

into your index.php

what you would expect is:

less than a minute ago

less than a minute ago

Today 11:21:16

Today 12:21:16

but what you get is:

less than a minute ago

less than a minute ago

less than a minute ago

less than a minute ago

the reason for this is, from the current code:

		if ($delta <= 3600 && ($delta >= -5 || (($now / 60) % 60) == (($gmepoch / 60) % 60)) && $date_cache[$format]['is_short'] !== false && !$forcedate && isset($this->lang['datetime']['AGO']))

$delta is -3600 and -7200 so both times <= 3600 and (($now / 60) % 60) == (($gmepoch / 60) % 60) is also true, as they are the same minute (doesn't care about the hour yet).

two possibilities I'd suggest:

• Remove detecting the minute, so it's only displayed as "less than a minute ago, when it is ago or the 5 seconds in future:

  if ($delta <= 3600 && ($delta >= -5) && $date_cache[$format]['is_short'] !== false && !$forcedate && isset($this->lang['datetime']['AGO']))

• or if you want to keep the detecting of the whole minute (which I think is wrong, as it may still take 59 seconds in some cases ) add a "$delta > -60 &&" to the minute-check:

  if ($delta <= 3600 && ($delta >= -5 || ($delta > -60 && (($now / 60) % 60) == (($gmepoch / 60) % 60))) && $date_cache[$format]['is_short'] !== false && !$forcedate && isset($this->lang['datetime']['AGO']))

  
  I'd prefer the first version.