Question

With this script

getFormattedTime = function (fourDigitTime){
var hours24 = parseInt(fourDigitTime.substring(0,2));
var hours = ((hours24 + 11) % 12) + 1;
var amPm = hours24 > 11 ? 'pm' : 'am';
var minutes = fourDigitTime.substring(2);

return hours + ':' + minutes + amPm;
};

I can change 4 digit time to normal clock time (there is a problem with 0930 though..)

And with this

$("body").html($("body").html().replace(/1135/g,'11:35am'));

To replace any occurange of 1135 in my page.

However, in my page, I have a list of time in tables. I need to convert them e.g.

Class starts at 1700, please be there by 1630 and sign in by 1645.

It should translate into

Class starts at 05:00pm, please be there by 04:30pm and sign in by 04:45pm.

Answer 1

Assuming the only digits displayed in the text are the times you can use:

var txt = 'Class starts at 0845, please be there by 1630 and sign in by 1645.'

getFormattedTime = function (fourDigitTime) {
    var hours24 = parseInt(fourDigitTime.substring(0, 2),10);
    var hours = ((hours24 + 11) % 12) + 1;
    var amPm = hours24 > 11 ? 'pm' : 'am';
    var minutes = fourDigitTime.substring(2);

    return hours + ':' + minutes + amPm;
};
/* replace numeric entities*/
var newTxt = txt.replace(/(\d+)/g, function (match) {
    return getFormattedTime(match)
})
$('body').html(newTxt);

DEMO : http://jsfiddle.net/q6HC9/1

EDIT: Wrapping times in a tag would greatly simplify situation. Wrap all military times in a span with a common class and then use the html() method

<span class="mil_time">0845</span>

getFormattedTime = function (fourDigitTime) {
    /* make sure add radix*/
    var hours24 = parseInt(fourDigitTime.substring(0, 2),10);
    var hours = ((hours24 + 11) % 12) + 1;
    var amPm = hours24 > 11 ? 'pm' : 'am';
    var minutes = fourDigitTime.substring(2);

    return hours + ':' + minutes + amPm;
};
/* find all spans and replace their content*/
$('span.mil_time').html(function( i, oldHtml){
   return getFormattedTime(oldHtml);
})