I've bumped into an odd result with the date() function that I can't make sense of. Starting with a unix timestamp for 31 December 2012 13:12:12 (which is 1356952332) I calculate a week number: $ux_date = 1356952332; $weeknumber = date("W", $ux_date); // returns 01 instead of 52 I found some warnings regarding ISO8601 for this in the user notes for the date() function in the PHP manual but couldn't see how this is managed in code, does anyone know of a workaround for this? Cheers Arno