If you have problems signing in to ADFS 2.0 who can be used with Office 365 and the on premise federation service, then check the time on the proxy servers. It shall have the same time as the internal federation servers.
You can use the below commands on the proxy servers to configure the time service, so that it get the time from the domains PDC emulator. (remember to open for NTP udp/123 on the firewall).
net stop w32time
w32tm /config /syncfromflags:manual /manualpeerlist:IP-FOR-THE-PDC-EMULATOR
net start w32time
w32tm /config /update