A.T. Robertson Commentary 1 Thessalonians 5:1

"But concerning the times and the seasons, brethren, ye have no need that aught be written unto you." — 1 Thessalonians 5:1 (ASV)

But concerning the times and the seasons (περ δε των χρονων κα των καιρων). See both words used also in Tit 1:2f. Χρονος is rather an extended period and καιρος a definite space of time.