"Last Client Login Time" vs "Last login time"

Hello Members,

What is the difference between

GWAC, user object, Diagnostics, Information, Last Client Login Time


GWAC, user object, User Mailbox, Statistics, Last login time.

The latter looks like an up to date last login time. But Last Client Login Time looks like an outdated something. I couldn't find anything in the documentation about this. I assume "Last login time" is something new and "Last Client Login Time" is there for backward compatibility.