If you look through the transaction pages on Baseball-Reference.com, sometimes patterns emerge, like particular general managers dealing with each other more often or certain teams making most of their significant moves in a certain time period.
One thing in particular stood out to me when Theo Epstein was named the Cubs’ president of baseball operations back in 2011, was Epstein almost always makes a deal at the non-waiver trade deadline. He made a deadline deal as a buyer on July 30 or July 31 in all 10 of his seasons in Boston. He was a deadline seller in two of his first three seasons with the Cubs, and a buyer last year.