Sony has forewarned PS3, PS4 and PS Vita users that there will be an eight-hour period of network downtime between Monday, December 9 and Tuesday, December 10.
It was flagged up in this tweet today:
Heads up > There will be Network maintenance on PSN – Monday 9th/Tuesday & 10th Dec between 16:00 and 00:00 GMT. Thanks for your patience.
— PlayStation Europe (@PlayStationEU) December 6, 2013