doc: use UTC for time references

doc/src/dev/contrib/contrib.md

@@ -6,7 +6,7 @@
 2. See the areas of work below. Good areas to get started are with
    tooling, Python bindings, p2p apps like the DHT.
 
-Every monday 16:00 CET, there is our main dev meeting on
+Every monday 15:00 UTC, there is our main dev meeting on
 [our chat](https://darkrenaissance.github.io/darkfi/misc/darkirc/darkirc.html).
 Feel free to join and discuss with other darkfi devs.
 
@@ -259,7 +259,7 @@ Check `README.md` for instructions.
 
 Join our DarkIRC chat and ask to speak with the core team.
 
-Usually the best time would be our weekly Monday meetings at 16:00 CET.
+Usually the best time would be our weekly Monday meetings at 15:00 UTC.
 
 If it's sensitive and time critical, then we will get in touch over DM,
 and we will post a message on dark.fi to confirm our identity once we're in

doc/src/philosophy/meetings.md

@@ -1,6 +1,6 @@
 # Discussion group
 
-Every other Wednesday at 16:00 CET/14:00 UTC/10:00 EST, there is a meeting on 
+Every other Wednesday at 14:00 UTC/16:00 CET/10:00 EST, there is a meeting on
 [darkirc](https://darkrenaissance.github.io/darkfi/misc/darkirc/darkirc.html) in 
 `#philosophy`.  Come and discuss different philosophy texts with fellow
 community members.

doc/src/start-here.md

@@ -36,7 +36,7 @@ and our core community organizes through our own fully anonymous p2p chat system
 which has support for Tor (and Nym waiting for 
 [this feature request](https://github.com/nymtech/nym/issues/3610)).
 
-Every Monday at 16:00 CET in #dev we have our main project meeting.
+Every Monday at 15:00 UTC in #dev we have our main project meeting.
 
 See the guide on [darkirc](misc/darkirc/darkirc.md) for instructions on joining.