Was it allegedly from the IRS? If so, government workers (if you want to call them that) do not work on weekends, holidays, or in the middle of the night. They do not call you, they send you letters in the mail delivered by the mailman. If this was a debt collection scam, no debt collector can issue a warrant, and if a warrant is issued, they do not call you and tell you about it, they simply come pick you up. Ignore the call and block the number as this is nothing more then a scam to steal money from you.