MaxG:
I was thinking of not using any library for the DS3231 (I think I remember it chewed up an extra 2k)...
2k sounds a lot, but I have seen the use of libraries being rather inefficient. I just want time so I stick with
http://bildr.org/2011/03/ds1307-arduino/
No change was required in order to use the DS3231. I use the same as in reply #8, and start a new file at midnight.