CSV Timeline files

Hi Colin

I've been looking at the timeline files a little more closely and was wondering if you could help me out with the following:

Are dates always included in the yy-mm-dd format where yy can be 2 or 4 digits, and the month and day are optional?
What is the difference between the importance and Timeline fields?

I assume that the following fields are lists of reference data as opposed to free text fields:
Importance
Timeline
Type
Flags

Can you remind me the meaning of the following fields too?
Flags (EY/EM)
Certainty
ID (was this just for you or are they cross-referenced across timelines)

Thanks
Chris