Mine was always 12 days. You can't really tell what it is unfortunately until you've been charting for a few months to see the pattern emerge.

Generally your LP will not chnge more than a day or so. Ovulation date however can, so if you think last time was about 12 days long then you could expect this one to be 11-13 days long & the cycle to be shorter than last time.

Does that make sense?!