The dat/ directory contains:

diary.dat: The diary. 3 lines per day.

29 Aug 2
# That is, 29th August, today's rating = 2/5
OK
# How feel on waking = OK
Comments
# Further comments on the day

sleep.dat: The sleep diary, one line per entry, contains:
(a) Time tried to get to sleep
(b) Time got to sleep
(c) Time woke.

29 Aug 23 00 30 Aug 01 00 30 Aug 09 00
breaks down into:
29 Aug 23 00 # started trying to sleep at 11pm
30 Aug 01 00 # got to sleep at 1am
30 Aug 09 00 # woke at 9am

other.dat
Anything else worth noting - caffeine, drugs, work, lightbox, etc.
lightbox 29 Aug 10 00 29 Aug 11 00 # Used lightbox on 29th August from 10-11am.
work 29 Aug 11 30 29 Aug 19 00 # Worked 29th August from 11:30am to 7pm.