Problem with default starting year 1921

[Sinaasappel]

I started the game with the default starting year of 1921, but it has a more or less serious problem: In the DB XL set, the train with the earliest build year is 1921. So the game may select this train as for 'exclusive usage', but will only do so somewhere mid 1921, so the first few months you won't have a train to use.

Anyways, i just found out that the default starting year is 1930 and not 1921, so the problem is less serious than i thought, but i'd like to point it out anyhow

[Hyronymus]

It's not a bug, it has to do with randomness. Year of introduction is the specified amount of months since 1921 (specified in NFO) plus some random factor which I forgot. So your next 1921-game may very well have an engine there.

[Oracle]

It's a randomness factor of 0 to 511 days on top of the number of days since 1920 specified as the introduction date, according to newgrf.txt.
Hyronymous is right, but it depends on when exactly MB has set the introduction date for.