How to round the minute of a timestamp to increments of 15?

I'm building an application to record when my cat has an asthma attack. I'm not interested in the exact time since glancing at the time in interval of 15 minutes is easier to review (e.g. roundin开发者_StackOverflowg 9:38am should be recorded as 9:45am).

I looked for a UDF at cflib.org for this but couldn't find one. I tinkered with CF's round function but I'm not getting it to do what I want.

Any advice?

This could do with a bit more polish (like data type validation) but it will take a time value and return it rounded to the nearest 15-minute increment.

<cfscript>
function roundTo15(theTime) {
    var roundedMinutes = round(minute(theTime) / 15 ) * 15;
    var newHour=hour(theTime);
    if (roundedMinutes EQ 60) {
        newHour=newHour + 1;
        roundedMinutes=0;
    }
    return timeFormat(createTime(newHour,roundedMinutes,0),"HH:mm");
}
</cfscript>

I'm not familiar with the format of the timestamp here, but generally when I want to round I do something like floor((val + increment / 2) / increment) * increment

I like Al Everett's answer, or alternatively store the actual time to preserve the most accurate time, then use query of query in the view and use between :00 and :15 to show the time in 15min period.

If you use Henry's suggestion to store the precise time in the database (principle: if there's no cost, prefer to preserve data), then you can simply use Al Everett's rounding function whenever you display the data to the user.