datetime InputFormat is returning month for minutes

I'm very confused by the behavior of the datetime InputFormat string in MATLAB.

I have a date string such as "2025040901:42:23 PM"

I believe I am correctly using MM for two-digit month and mm for twelve-hour two-digit minutes. Why is the month always being returned as the minutes?

>> s = "2025040901:42:23 PM"
s = 
"2025040901:42:23 PM"
>> datetime(s, 'InputFormat', 'yyyyMMddhh:mm:ss a')
ans = 
datetime
2025-04-09 13:04:23

Change the month to prove that that is what is being shown.

>> s = "2025060901:42:23 PM"
s = 
"2025060901:42:23 PM"
>> datetime(s, 'InputFormat', 'yyyyMMddhh:mm:ss a')
ans = 
datetime
2025-06-09 13:06:23

Answer 1

[Fangjun Jiang]

It is correct running your code here in R2024b.

s = "2025040901:42:23 PM";
datetime(s, 'InputFormat', 'yyyyMMddhh:mm:ss a')

ans = datetime
   09-Apr-2025 13:42:23

s = "2025060901:42:23 PM";
datetime(s, 'InputFormat', 'yyyyMMddhh:mm:ss a')

ans = datetime
   09-Jun-2025 13:42:23

[Scott]

Thank you. Yes, I tried it on another installation and it worked fine there. Something must be weirdly corrupted on this system. Thank you for checking it out.

Answer 2

[Scott]

And to follow-up, I found that my preferences for the default date and time format (Preferences, MATLAB, Command Window) was mistakenly using "MM" for minutes, as in:

So the underlying data was correct, it was the display of the data that was incorrect. I don't know how this preference got set, but I'll take the blame for now.