To fix your 200 or so cells you can try this:
- Make a backup copy of your work first!
- Copy-paste the script below into Script Editor (in Applications > Utilities)
- Select the 200 cells containing the dates in the format you posted. (This assumes they're all in that same format).
- With the cells selected, click the triangle 'run' button in Script Editor.
This should convert the cells to true date-time strings displayed in YYYY-M-D format or as text in YYYY-MM-DD format. Then go to Data Format panel and format them as YYYY-MM-DD.
If the script throws off an error post with specifics and I will modify. You should first check that you have Script Editor checked at System Preferences > Security & Privacy > Privacy > Accessibility.
Note that you don't need AppleScript knowledge or experience to try this, but I'll need specifics of the problem if you encounter one.
SG
tell application "Numbers"
tell front document's active sheet
tell (first table whose selection range's class is range)
repeat with c in (get selection range)'s cells
set v to c's value
set yyyy to v's first word
set dd to v's third word
set mm to my monthNameToNum(v's second word)
set c's value to yyyy & "-" & mm & "-" & dd
end repeat
end tell
end tell
end tell
to monthNameToNum(theMonth)
set monthList to {January, February, March, April, May, June, July, August, September, October, November, December}
repeat with i from 1 to 12
if theMonth = ((monthList's item i) as string) then
set monthNum to (text -2 thru -1 of ("0" & i))
return monthNum
end if
end repeat
end monthNameToNum
