first_blast_furnace, world_is_round, and gunpowder_discovered

I'm editing descr_events.txt in M2TW 1.3 Vanilla and basically I'm just trying to have gunpowder units (both men and siege) appear later than normal because I like my traditional arrow combat and I like having fortifications remain strong.

I know how to edit the gunpowder_discovered parameter, but I need to know if making the date of the discovery later than first_blast_furnace or world_is_round would cause a problem. Please also let me know if there's any other event consistency I need to watch out for.

And what does first_blast_furnace do anyway?

I haven't played the game yet. Thanks in advance :)

Blast furnace is just a message. Does nothing.

You can put gunpowder whenever you want, including past the end date in descr_strat. You want to tie gunpowder mercenaries' recruitment dates to it though (descr_mercenaries).