1 Thess 5:2-4
"For you yourselves are fully aware that the day of the Lord will come like a thief in the night. When people say, ‘Peace and safety!’ then sudden destruction will come upon them... but you are not in darkness, brothers, for that day to surprise you like a thief."
The Day of the Lord will come unexpectedly for those who are in darkness. But believers are 'children of light'—they will not be caught off guard. Preparation is not about calculating dates, but living in watchfulness and sobriety.