Setting the random seed using Year-Month-Date

Can any one please explain how this 1986 came up from

December 20, 2018: 2018 − 12 − 20 = 1986 which was used in



Can you supply some code for what you are doing?

This *December 20, 2018: 2018 − 12 − 20 = 1986 * seems meaningless in R

set.seed can be any number, it doesnt matter what it is aside from that if you want to repeat the same run with the same randomization, the set seed number should be the same.
When people are free to choose random seed numbers, they will do what pleases them.
I usually go with set.seed(42) because 42