A small AppleScript to take a screenshot every X minutes and run for Y hours. Saves to an Image with datetime to your specified folder. Great for recording your workday.

ScreenshotTimer.scpt

set dir to "~/Dropbox/Dropbox2/ScreenshotTimer/"
do shell script ("mkdir -p " & dir)

set intervalMins to 15 -- Change as per your desired frequency (in minutes)
set durationHours to 8 -- Change as per your desired duration (in hours)

-- Convert minutes to seconds for screenshot interval
set intervalSecs to intervalMins * 60
-- Calculate total repetitions within duration
set totalReps to durationHours * 60 / intervalMins

repeat totalReps times
	set {year:y, month:m, day:d, hours:h, minutes:min, seconds:s} to (current date)
	set dayStr to text -1 thru -2 of ("00" & d)
	set monStr to text -1 thru -2 of ("00" & (m * 1))
	set dateTime to (y & "-" & monStr & "-" & dayStr & "_" & h & "-" & min & "-" & s) as string
	tell application "System Events"
		set openWinsCount to count (every window of every process)
		if openWinsCount > 0 then
			do shell script ("screencapture " & dir & dateTime & ".png")
		end if
	end tell
	delay intervalSecs
end repeat