If you're looking to format many timestamps all at once, I've written a C util called datefmt that formats timestamps in a text stream:
Let’s say we have some logs that contain unix timestamps:
$ cat logs.txt
EVENTS  1638499687   blahblah log1
EVENTS  1638499717   blahblah log2
We can pipe this log into datefmt to convert these timestamps into human-readable dates:
$ <logs.txt datefmt
EVENTS  2021-12-02 18:48   blahblah log1
EVENTS  2021-12-02 18:48   blahblah log2
Of course you can customize the format as well:
$ <logs.txt datefmt "DATE:'%m-%d %R'"
EVENTS  DATE:'12-02 18:48'   blahblah log1
EVENTS  DATE:'12-02 18:48'   blahblah log2
I've packaged this in NixOS, hopefully it will trickle out to other distros soon, but for now you will need to download the tarball and build it with make