Convert current time in the next half hour

Question

I have a list of times displayed as radio buttons. I would like to use JavaScript to select the user closest to the current time. I already use jquery on my site (if that matters). In addition, I have another set of switches that I would like to select by default for +3 hours from the "Earliest acceptable time."

<label for="select-choice-etime">Earliest acceptable time:</label> <select name="select-choice-etime" id="select-choice-etime"> <option value="12:00 AM">12:00 AM</option> <option value="12:30 AM">12:30 AM</option> <option value="1:00 AM">1:00 AM</option> <option value="1:30 AM">1:30 AM</option> <option value="2:00 AM">2:00 AM</option> <option value="2:30 AM">2:30 AM</option> <option value="3:00 AM">3:00 AM</option> <option value="3:30 AM">3:30 AM</option> <option value="4:00 AM">4:00 AM</option> <option value="4:30 AM">4:30 AM</option> <option value="5:00 AM">5:00 AM</option> <option value="5:30 AM">5:30 AM</option> <option value="6:00 AM">6:00 AM</option> <option value="6:30 AM">6:30 AM</option> <option value="7:00 AM">7:00 AM</option> <option value="7:30 AM">7:30 AM</option> <option value="8:00 AM">8:00 AM</option> <option value="8:30 AM">8:30 AM</option> <option value="9:00 AM">9:00 AM</option> <option value="9:30 AM">9:30 AM</option> <option value="10:00 AM">10:00 AM</option> <option value="10:30 AM">10:30 AM</option> <option value="11:00 AM">11:00 AM</option> <option value="11:30 AM">11:30 AM</option> <option value="12:00 PM">12:00 PM</option> <option value="12:30 PM">12:30 PM</option> <option value="1:00 PM">1:00 PM</option> <option value="1:30 PM">1:30 PM</option> <option value="2:00 PM">2:00 PM</option> <option value="2:30 PM">2:30 PM</option> <option value="3:00 PM">3:00 PM</option> <option value="3:30 PM">3:30 PM</option> <option value="4:00 PM">4:00 PM</option> <option value="4:30 PM">4:30 PM</option> <option value="5:00 PM">5:00 PM</option> <option value="5:30 PM">5:30 PM</option> <option value="6:00 PM">6:00 PM</option> <option value="6:30 PM">6:30 PM</option> <option selected="selected" value="7:00 PM">7:00 PM</option> <option value="7:30 PM">7:30 PM</option> <option value="8:00 PM">8:00 PM</option> <option value="8:30 PM">8:30 PM</option> <option value="9:00 PM">9:00 PM</option> <option value="9:30 PM">9:30 PM</option> <option value="10:00 PM">10:00 PM</option> <option value="10:30 PM">10:30 PM</option> <option value="11:00 PM">11:00 PM</option> <option value="11:30 PM">11:30 PM</option> </select> 

Answer 1

Here, a function is used to convert the current time to the next half hour in the form used in your parameters (for example, the nearest time is "10:30 PM"), and then a way to use this time to select the desired option.

 function getNearestHalfHourTimeString() { var now = new Date(); var hour = now.getHours(); var minutes = now.getMinutes(); var ampm = "AM"; if (minutes < 15) { minutes = "00"; } else if (minutes < 45){ minutes = "30"; } else { minutes = "00"; ++hour; } if (hour > 23) { hour = 12; } else if (hour > 12) { hour = hour - 12; ampm = "PM"; } else if (hour == 12) { ampm = "PM"; } else if (hour == 0) { hour = 12; } return(hour + ":" + minutes + " " + ampm); } 

You can choose your preferred option:

 // remove any previous selection $('#select-choice-etime option').removeAttr('selected'); // select the one that matches the current time $('#select-choice-etime option[value="' + getNearestHalfHourTimeString() + '"]').attr('selected', 'selected');​ 

You can see how it works here: http://jsfiddle.net/jfriend00/Zz7pW/

Answer 2

Assuming you want to round minutes to the nearest 00/30/60, you can use the ceiling function:

 var now = new Date(); now.setMinutes(Math.ceil(now.getMinutes() / 30) * 30); // Test cases: // Math.ceil( 0 / 30) * 30 = 0 // Math.ceil( 1 / 30) * 30 = 30 // Math.ceil(30 / 30) * 30 = 30 // Math.ceil(31 / 30) * 30 = 60 // Math.ceil(59 / 30) * 30 = 60 // // Note that setMinutes(60) increments the hour and sets the minute equal to zero var h12h = now.getHours(); var m12h = now.getMinutes(); var ampm; if (h12h >= 0 && h12h < 12) { if (h12h === 0) { h12h = 12; // 0 becomes 12 } ampm = "AM"; } else { if (h12h > 12) { h12h -= 12; // 13-23 becomes 1-11 } ampm = "PM"; } var timeString = h12h + ":" + ("00" + m12h).slice(-2) + " " + ampm; $("#select-choice-etime").val(timeString); 

Note: replace ceil with a circle on the map of minutes 00 ... from 14 to 00, from 15 ... 44 to 30 and from 44 ... 59 to 60.

Demo here

Answer 3

There! This will help you get started:

 var time = new Date(), hours = time.getHours(), minutes = (time.getMinutes().length < 2) ? time.getMinutes() : '0' + time.getMinutes(); ampm = 'AM'; if (hours.match(/[13-23]/)) { ampm = 'PM'; } // You have to convert 13 to 1, 14 to 2 etc. 

Answer 4

This parameter is based on GMT tz=GM in the query string:

 $(document).ready(function() { $.getJSON("http://json-time.appspot.com/time.json?tz=GMT&callback=?", function(data) { var GMT3 = data.hour; // data.hour+3 (if you want to use GMT+3 if (data.minute < 15) { alert("Current Time is: " + GMT3 + " Selected is " + GMT3 + ":00"); } else if (data.minute < 45) { alert("Current Time is: " + GMT3 + " Selected is" + GMT3 + ":30"); } else { alert("Current Time is: " + GMT3 + " Selected is" + GMT3 + 1 + ":00"); } }) });​ 

The getJSON method returns:

 { "tz": "GMT", "hour": 8, "datetime": "Thu, 01 Mar 2012 08:12:25 +0000", "second": 25, "error": false, "minute": 12 } 

Answer 5

You can check this code first.

 var now = new Date(); var hour = now.getHours(); var min = now.getMinutes(); var ext = hour > 11 ? 'PM' : 'AM'; var tempRes = $("<select>"); // first we select all PM or AM and append to temp element $("#select-choice-etime > option[value$='" + ext + "']").appendTo(tempRes); // and then we select current hour elements within PM or AM var result = tempRes.find("option[value^='" + hour + "']"); // finally we have two elements in result variable // for example if hour is 10:12 PM // result has two items which are 10:00 PM and 10:30 PM // // i think you can solve from there