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# How to calculate time elapsed for AM and PM

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Mekala balaji on 19 Mar 2018
Commented: Mekala balaji on 19 Mar 2018
Hi,
I have below time array:
Start time End time
23:12:17 PM 23:12:19 PM
3:12:11 AM 3:12:29 AM
23:59:17 PM 01:10:13 AM
11:59:17 AM 13:10:13 PM
I want to calculate time elapsed between Start time to End time of each row.

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### Answers (2)

Image Analyst on 19 Mar 2018
See the help for etime().

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Mekala balaji on 19 Mar 2018
Sir, it give negative value when it turn PM to AM (row 3) or AM to PM (row4)
Image Analyst on 19 Mar 2018
If the time is negative, add 24 hours to it.
Mekala balaji on 19 Mar 2018
Sir,
I tried as below, but it seems some problem,
t1={'23:59:00 PM'}
t1 =
cell
'23:59:00 PM'
>> t2={'00:1:00 AM'}
t2 =
cell
'00:1:00 AM'
>> t2={'12:1:00 AM'}
t2 =
cell
'12:1:00 AM'
>> t1=datevec(t1)
t1 =
2018 1 2 11 59 0
>> t2=datevec(t2)
t2 =
2018 1 1 0 1 0
>> etime(t2,t1)
ans =
-129480

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Star Strider on 19 Mar 2018
You should add dates to each time, and delete the ‘AM’ and ‘PM’ since you are also using 24-hour times.
Try this:
SA = {'23:12:17' '23:12:19'
'3:12:11' '3:12:29'
'23:59:17' '01:10:13'
'11:59:17' '13:10:13'};
DA = datetime(SA, 'InputFormat','HH:mm:ss');
BT = between(DA(:,1), DA(:,2));
It will give a negative value for Row 3, because the between function does not ‘know’ they are consecutive days, since you did not tell it.

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