"TS" is the channel's creation timestamp. It is usually shown in readable format when you join the channel, or when you use
(The large number is a "Unix timestamp"; number of seconds since 1970-01-01.
1272500695 is 2010-04-29 00:24:55.)
In your situation, the message can be translated as:
You have joined an empty channel. As the first person in it, you become a chanop.
However, the channel is still owned (registered) by someone else. Services will now remove your chanop status.
Netsplits – the original purpose of timestamps
If the network splits in two and the channel ends up with no people on one side, it automatically gets destroyed (as usually happens with empty channels). Any random person trying to join that channel would re-create it and automatically become a chanop (channel operator).
When the network gets re-linked, it needs to merge these two identically named channels from both sides. If their creation times are also identical, then they must be two halves of the same channel, and their user lists merged.
However, if the channel coming from one side has a newer timestamp, that means it was re-created; the chanop status of everyone from that side is considered illegitimate and automatically removed.
Services – the trick you are currently seeing
When you join and re-create a channel which had been previously registered with network services, the services software fakes a similar event in order to remove chanop status of everyone who joined. It is a faster and more reliable method than rushing to send regular
/mode -o commands.
As an added bonus, this makes
/mode #chan show the correct time of when the channel was originally created and registered.