Time sheets

It's that time of the month when I need the time sheets so we can pay the guys. For most of them this is not a problem. But for one fellow co. worker (idiot?) this seems to be a major challenge.You have to start reminding him a week before you need them so he can come up with the goods. This morning out he wanders with his diary, now you would think he would have it all written in there but NO. What date did this month start on? Which Saturdays have I worked, Did I do any extra time? is this a four or five week month? It really isn't that difficult is it? even if you don't fill it in every day the time sheet is a simple piece of paper. None of the other guys have a diary to write in, they do differant hours every day/week, but the fellow co. worker (idot?) who has the most problelm with the time sheets works 9-5 four days a week and one saturday in every three HOW CAN HE NOT WORK IT OUT?