You can turn on the timestamp by going into the Invision menu, then Main Settings. Click the ADV tab and look in the top, left corner. You'll see a box for the timestamp. Set it up the way you want (blank will mean no timestamp).
How to format the timestamp box:
HH == 2-digit hours (in 24 hour format) -- 05 or 13 or 18
hh == 2-digit hours (in 12 hour format) -- 04 or 08 or 12
H == 1 and 2-digit hours (in 24 hour format) -- 5 or 13 or 18
h == 1 and 2-digit hours (in 12 hour format) -- 4 or 8 or 12
nn == 2-digit minutes -- 03 or 15 or 49
n == 1 and 2-digit minutes -- 3 or 15 or 49
ss == 2-digit seconds -- 06 or 11 or 58
s == 1 or 2-digit seconds -- 6 or 11 or 58
tt == am or pm
t == a or p (same as above, but no "m" after a/p)
Examples:
[hh:nn:sstt] == [05:37:12pm]
[H:nn] == [14:24]
-=h:nntt=- == -=7:12am=-
If you want to also include date information, here is the information for dates:
m == month (mm == 2-digit months, just like with time above)
d == day (dd == 2-digit days, ddd == Mon, Tue, etc., dddd == Monday, Tuesday, etc.)
yy == 2-digit year (yyyy == 4-digit year)