The two are interrelated. Charles Taze Russel (founder of what is now called the Jehovah’s Witnesses) was associated with the Millerites. Lots of their doctrine was copied from the 7th Day Adventists, including the numerology of the timeline that gets them to 1914 as “the” year. That one was supposed to be just a step along the way, but after WWI happened, it was a lot of pointing and saying “see, we predicted something big would happen”.
The two are interrelated. Charles Taze Russel (founder of what is now called the Jehovah’s Witnesses) was associated with the Millerites. Lots of their doctrine was copied from the 7th Day Adventists, including the numerology of the timeline that gets them to 1914 as “the” year. That one was supposed to be just a step along the way, but after WWI happened, it was a lot of pointing and saying “see, we predicted something big would happen”.