Time terminology

I'm a bit lost with time terminology.

I understand what epoch is and the difference between GMT and UTC.

However I'm a bit confused about the following notations:

calendar time
local time
wall time

How are these related to timezones and daylight savings?

P.S. Good link (thanks to @ZincX)

How do you say time in a formal way?

In formal contexts, we use a.m. and p.m. to specify whether a time is before or after midday (mostly UK) / noon (mostly US): 4:00 four a.m. (note that you shouldn't say 'o'clock' with these abbreviations).

Calendar time is the time that has elapsed since the epoch (t - E).
Local time is calendar time corrected for the timezone and DST.
Wall time: I assume you mean wallclock time. This it the time elapsed since a process or job has started running.

RTFM time(7), localtime(3), time(1).