what are the appropriate date and time prepositions

Question

In English you can meet
at a time (We will meet at 4pm.)
on a date (We will meet on the 4th.)
or be on time.

Esperanto doesn't seem to have quite the same rules. Is it en a date and je a time? What about being "on time" ?

Answer 1

In general you use je for a time and the -n suffix for a date. Eg:

Ni renkontiĝu je la 4a posttagmeze / je la 16a → Let’s meet at 4pm

Ni renkontiĝu la 4an (de januaro) → Let’s meet on the 4th (of January)

There is more detailed information about times and dates in PMEG.

I think you would only use en if you are talking about a non-specific point within a certain time range. Eg,

Ni renkontiĝu en januaro → Let’s meet (at some point) in January

PMEG has some information about this too.

For “on time” you can say ĝustatempe.

Venu ĝustatempe aŭ ni maltrafos la komencon de la filmo.

Answer 2

Both je and the accusative -n (without preposition) are correct for specific points in time, indiscriminate for times and dates. The accusative also for other prepositions like dum. The preposition en is used too, for a point inside a larger range.

esti ĝustatempe = to be on time

dum la oka de marto ne forgesu gratuli vian edzinon = on the 8th of March do not forget
                                                      to wish your wife well
dum la tria horo ili dormis = they slept around three

The preposition dum for what actually is a period.

dum la semajno = in/during the week
en la semajno = at some point in the week

The usage of dum seems preferable, but en is found too. The distinction above I just made up, and is not prescriptive.

Other prepositions:

post tempo = in time all will become alright