Afghan medallions

[FosseWay]

With 'divided date' I mean that there is space between the first 2 figures of the date and the last 2, like this: ۱۳  ۱۲
I have observed that on more medals and thought there might be some sort of reason for it.

Oh, I see - with you now 

I don't think there's any significance in it, to be honest. The date is also not centred in relation to the wreath, so I suspect it's just carelessness.

[FosseWay]

I wish all arab countries would just use the same calendar.

Being pedantic for a moment, neither Afghanistan nor Iran are Arabic countries. The majority groups in both countries speak Indo-European languages.

I don't know whether the choice of solar vs lunar is connected with either ethnicity or with religious denomination (Sunni vs Shia) or is just random.

[Figleaf]

Both systems have their advantages and disadvantages. A sun-based calendar makes a connection between the calendar and the seasons, important for food farming, as it becomes easier to figure out planting time and harvest time (at the cost of a leap day every four years). A moon-based calendar is better for animal raising as in many animals (as well as humans) the period of pregnancy is easier to express in moon months. Since assistance at the time of delivery enhances the chances of mother and child, it is important to have a pretty good idea of when that assistance will be needed.

Peter

[Pabitra]

Being pedantic for a moment, neither Afghanistan nor Iran are Arabic countries. The majority groups in both countries speak Indo-European languages.

I don't know whether the choice of solar vs lunar is connected with either ethnicity or with religious denomination (Sunni vs Shia) or is just random.

AH originated from Saudi Arabia and is followed all over Arabic states right upto countries like Morocoo, Tunisia & Libya. It followed the propagation of Islam.
Libya, for a short period, followed another era, named MD.
Egypt, though not calling themselves Arabs and using Egyptian language, continues to follow AH as calendar system.
Algeria, in a recent coin, has started using Berber era and it is expected to use that in new series circulation coins.

Propagation of Islam towards east of Saudi Arabia, resulted in neither Arabic nor AH being followed in Iran and Afghan where languages like Persian, Pushtu etc are in use and are of Indo European in origin ( as already indicated).The era used is SH.

 However, further east, Indian Princely states, especially under Mughal influence, primarily followed Persian but calendar used was AH.