Current Event Guide

Alt Tag

General Guides

6_lasers - Reddit guide guy. Overview, shop info, and general advice.
Blue Archive Wiki - Link to the event information on the wiki.

Additional Tools

Event Planners

justin - In English. Updated whenever he feels like it, usually around the event date on global but sometimes is pretty late with it.

/bag/ fork - A fork of Justin's planner made by a /bag/ anon, more features and actually up to date, you're likely better off using this instead.

arona.ai - In Korean. Updated 6 months early, usually alongside the original event release in JP.

I'll try, but no promises of keeping this up to date, bookmark the page or not, up to you.
If you're using the Alt Tag extension Alt Tag you can tell easily, if it's there it's updated if it's not there then it's not.