Well, he's coming this January, if you want him now NOW.
But I'm pretty sure he's getting a banner later in the year, so I'm saving for that one. This video gives all the summon banners this year.
https://www.youtube.com/watch?v=--K3qlP8ga0&t=642s&list=LL8VVYWWGi21Su6invcP3KXQ&index=4
Good luck!
His banner should be the next one after Musashi. I'm assuming it'll be straight after so I think the 10th if Musashi banner ends on the 9th.
Gramps does have another banner later in the year but the only other rate up servants in that banner are Hassan of hundred personas and serenity so, unless you like them and don't have them np5, I'd advise rolling for gramps this month.
The reason I'm not rolling Musashi now is because on her banner later, there's 2 new rate up 4 star servants (archer and assassin) and a new 3 star lancer also on rate up.
