Well, a few months ago I noticed the battery in my Amiga4000PPC started to leak and so I removed it to avoid my A4k-mobo getting damaged.
I was still wondering if I should look for an replacement or not when I got aware of NetClock.
Once you go online with your Miggy, NetClock immediately starts, tries to contact an web-based time server and - if successful - sets your system time to the actual time (if necessary).
No longer need for batteries...