This is intended as a public service for all ESO players because January 2019 starts in approximately 6 hours...if you don't believe me, pull up your Announcements dialog and look at the timer right in the game.
At this point, the Daily Rewards gift is not a new thing, it has been running for several months now, and players have had ample time to adjust to the way that the monthly calendar is put into place. Yet even last month, players have complained about missing the last reward at the end of the month. One of the causes of this has been that some players do not yet comprehend the Time Zone effect of this function in the game. This game is, as most are, a global community MMORPG. That means that people around the world in essentially 24 different Time Zones are playing this game simultaneously. However, as it is a real-time game, time is an important function in the game, and the game cannot accommodate everyone's own personal local time, whatever that may be. Therefore, there is a global time frame that everything references back to, and it is based on UTC (Coordinated Universal Time, don't ask me why it's UTC). I think of it in general terms as local London time, although due to the same Time Zone reasons, especially Daylight Saving, this is also not always true.
Time Zones are different from each other, and Daylight Saving changes the time of day during periods of the year, but with the exception of periodic insertion of leap seconds to sync with GMT (Greenwich Mean Time, based on solar time) UTC is always exactly 24 hours, no more, no less. It is then incumbent upon the individual players to understand the translation between UTC and their own local time, so that they can stay "in sync" with whatever is going on in the game.
Most regular players will know what time the Daily quests reset, what time the Fencing timer resets, and other timed events. The Daily Reward is the same, and it's reset is every night at Midnight, UTC. People don't really have an issue with that, and translate to their own local times. However, what is different is that not only is there a daily timer, but also a monthly one. That is why the start of a new rewards calendar appears to some as a day early. And thus, depending on how many idle days in the monthly calendar or whatever other reasons, players may miss claiming the last daily reward or two.
So please, please, check your daily rewards TODAY! It just might make a difference at the end of January 2019 for you.