John Gill Commentary 2 Kings 15:13

"Shallum the son of Jabesh began to reign in the nine and thirtieth year of Uzziah king of Judah; and he reigned the space of a month in Samaria." — 2 Kings 15:13 (ASV)

Shallum the son of Jabesh began to reign in the nine and
thirtieth year of Uzziah king of Judah
The same with Azariah: he is sometimes called by one name, and sometimes by the other, see (2 Kings 14:21) ,

and he reigned a full month in Samaria :
and no longer; so soon were the conspiracy against his sovereign, and the murder of him, punished.