I am trying to run osmupdate but I keep getting an error.

E:\osmq>osmup.exe -v --day planet.o5m planet_new.o5m
osmupdate Parameter: --day
osmupdate Parameter: planet.o5m
osmupdate Parameter: planet_new.o5m
osmupdate: file planet.o5m has no file timestamp.
osmupdate: Running statistics to get the timestamp.
osmupdate: Aging the timestamp by 4 hours for safety reasons.
osmupdate: timestamp of planet.o5m: 2015-07-07T21:22:02Z
osmupdate: newest daily timestamp: (no timestamp)
osmupdate Error: Could not get the newest daily timestamp from the Internet.

Any ideas?

Maybe the planet.openstreetmap.org server is not available?

Does that updating work with smaller OSM files?

The server was available at the time. Did not try with a smaller file. I gave up osmupdate and use osmconvert “manualy” instead.