A droid forum suggests that this happened to people after they changed time zones on the phone. It happened several hours after I changed time zones, and I changed zones twice due to having a layover.

EDIT, THIS PARAGRAPH ONLY: Sure enough, if I scroll back 11 hours (I'm in a time zone 11 hours later than at home), I see the current messages. This is puzzling since IT WORKED for several hours, then decided to mess up. I do see one unifying factor, though: I've been in this country since about 9:15 last night, and all the messages are showing up just prior to a 9:30 message.

It would be nice if there were a master time changer! In the phone I have to change from/away from set by network; set it to a particular time zone; and type in the time (whether you've set it to a time zone or not).

On the laptop I was told dropbox would not sync because the time on the computer did not match the time on the... on the local network? I don't know where it figured out my local time. But there's that, then changing the time zone on google calendar.

It took me a day and a half to get everything synced up again on the last two trips. Meanwhile, I've synced the time zones but I'm still not seeing the newest messages.