Possible percent (”%”) substitions in log filename (XChat for Windows 2.6.1+)

   %n    est remplacé par le nom de réseau.
   %c    est remplacé par le nom du salon.

%a

  Abbreviated weekday name

%A

  Full weekday name

%b

  Abbreviated month name

%B

  Full month name

%C

  The century number (year/100) as a 2-digit integer.

%d

  Day of month as decimal number (01 - 31)

%D

  Equivalent to %m/%d/%y.

%e

  Like %d, the day of the month as a decimal number, but a leading zero is replaced by a space.

%F

  Equivalent to %Y-%m-%d (the ISO 8601 date format).

%H

  Hour in 24-hour format (00 - 23)

%I

  Hour in 12-hour format (01 - 12)

%j

  Day of year as decimal number (001 - 366)

%k

  The hour  (24-hour clock) as a decimal number (range  0 to 23); single digits are preceded by a blank. (See also %H.)

%l

  The hour (12-hour clock) as a decimal number (range  1  to 12); single digits are preceded by a blank. (See also %I.)

%m

  Month as decimal number (01 - 12)

%M

  Minute as decimal number (00 - 59)

%p

  Current locale's A.M./P.M. indicator for 12-hour clock

%P

  Like %p but in lowercase: "am" or "pm".

%S

  Second as decimal number (00 - 59)

%U

  Week of year as decimal number, with Sunday as first day of week (00 - 53)

%w

  Weekday as decimal number (0 - 6; Sunday is 0)

%W

  Week of year as decimal number, with Monday as first day of week (00 - 53)

%x

  Date representation for current locale

%X

  Time representation for current locale

%y

  Year without century, as decimal number (00 - 99)

%Y

  Year with century, as decimal number

%z, %Z

  Either the time-zone name or time zone abbreviation, depending on registry settings; no characters if time zone is unknown

Source : http://xchat.org/docs/log/