“It was a bright cold day in April, and the clocks where striking thirteen.”

This is the first line of the book and it sets the stage for what has changed and stayed the same from what they have been used to. The months seem to have remained the same since it is April and the location is cold. This is in a future still being built because there is people still remember the way before. The mouths have not changed because the month still exists. The thing is that the clock is turning thirteen. As of now we have two sets of 12-hour system making up our day. In this system the clocks have 13 hours or more making it seem different. This might also mean that military time has become the standard time. This would just mean that it is 1:00 in the afternoon.
One thing to keep in mind is that it is cold in April in a area located in current day London. London has the same weather patters as the US being we are in the same hemisphere. I always remember April as a warm month with no chance of rain in most locations. This means that the weather has been altered to create a ire mood for the reader to meet the protagonist of the story. This might have a subconscious effect on the population making them seem like the next day will be the same as the last day. The bright mentioned is to make the coldness disappear and seem like everything is fine in this futuristic civilization. This combination of weather seems like a unique commination. I would expect that people are used to this