utc maxi is nostr/crypto slang for a "maximalist" who sticks strictly to coordinated universal time (utc) to dodge timezone confusion, especially with global "gm" posts.

nostr:nevent1qqsv29a4p9h8ttv2p7zqqxuq9efx2h8gqhgjr2a60z6q9h4zkrqymq3p3yvm3l46v

source: nostr community lingo