A sub in form of transport that's dated (8)
I believe the answer is:
calendar
'that's dated' is the definition.
(I've seen this before)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for calendar that I've seen before include "that's dated" , "Year chart" , "Date chart" , "that's stuffed with dates" , "Table of months and days" .)