rounded time value with intervals

Im trying to convey the seconds since midnight into the format HH:MM PM (or AM). So far I have this:

secondsSinceMidnight = 26850.431

minuteInterval = 15

datestr(seconds(timestamp),'HH:MM PM')

The problem is that when it's an time like '7:27 AM', it needs to say '07:30 AM' ( i.e. have the zero in front and round up to closest 15 min interval).

How would I go about those two fixes?

Answer 1

[Voss]

Something like this might work for your purposes:

secondsSinceMidnight = 26850.431;
minuteInterval = 15;

% round *up* to next 15 minutes:
% timestamp = ceil(secondsSinceMidnight/60/minuteInterval)*minuteInterval*60;

% or round to *nearest* 15 minutes:
timestamp = round(secondsSinceMidnight/60/minuteInterval)*minuteInterval*60;

% make a character array via datestr():
str = datestr(seconds(timestamp),'HH:MM PM');

% datestr doesn't include leading 0 with AM/PM format (see documentation),
% so: manually put leading 0 in if necessary:
if str(1) == ' '
    str(1) = '0';
end
disp(str);

07:30 AM

Answer 2

[Cris LaPierre]

I think in this case, it's easiest to round the seconds to the closest 15-minute increment. This uses 24-hr time, so no AM/PM is necessary.

minuteInterval = 15;
secondsSinceMidnight = 26850.431;
% calculate the closest 15-minute increment
seconds15min = round(secondsSinceMidnight/minuteInterval/60)*minuteInterval*60; 
% Convert to a duratoin
t = seconds(seconds15min)

t = duration
   27000 sec

% format the time
t.Format = 'hh:mm'

t = duration
   07:30