[TERMS] What do these terms in Indico mean?

Yes.
But I think this remark brings us to another topic, which is the localisation. I see strings to be translated like “August” and “Monday” in transifex. This should certainly be managed by i10n, as date and number display are not a translation per se, and (some) code already exists in standard python libraries.

import locale
from datetime import datetime
d=datetime(2020,1,25,13,15)
[(locale.setlocale(locale.LC_ALL, i), d.strftime("%c %x")) for i in 
 ["en_US", "en_GB", "de_DE", "de_AT", "zh_CN", "zh_HK", "ja_JP", "ar_DZ", "ar_SY", "ar_SA"]]

yields

[
 ('en_US', 'Sat 25 Jan 2020 01:15:00 PM  01/25/2020'), 
 ('en_GB', 'Sat 25 Jan 2020 13:15:00  25/01/20'), 
 ('de_DE', 'Sa 25 Jan 2020 13:15:00  25.01.2020'), 
 ('de_AT', 'Sa 25 Jän 2020 13:15:00  2020-01-25'), 
 ('zh_CN', '2020年01月25日 星期六 13时15分00秒 2020年01月25日'), 
 ('zh_HK', '2020年01月25日 星期六 13:15:00 2020年01月25日 星期六'), 
 ('ja_JP', '2020年01月25日 13時15分00秒 2020年01月25日'), 
 ('ar_DZ', '25 جانفي, 2020  01:15:00 م 25 جانفي, 2020'), 
 ('ar_SY', '25 كانون الثاني, 2020  01:15:00 م 25 كانون الثاني, 2020'), 
 ('ar_SA', 'السبت 25 يناير 2020  13:15:00 السبت 25 يناير 2020')]
] 

(I think the LTR conversion is not always done well.) So there should be no need to translate strings like "%Y/%M/%D".

And ordinals (like 1st, 2nd) also fall in this category of “translation”. But I did not see any standard code for those yet. However I believe there are (or at least were) used in Indico.