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<title>The Time - Converting AM/PM to 24 Hour Clock</title>
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<h1 class="center">Time - AM/PM vs 24 Hour Clock</h1>
<div style="float:left; margin: 0 10px 5px 0;">
<iframe src="measure/iclock-digitalam.html" scrolling="no" style="width:202px; height:102px; overflow:hidden; margin:auto; display:block; border: none;"></iframe>
</div>
<p>Normally&nbsp;time&nbsp;is shown as <b>Hours:Minutes</b></p>
<p>There are 24 Hours in a Day and 60 Minutes in each Hour.</p>
<div style="clear:both"></div>
<div class="example">
<p>Example: <b><span class="larger">10:25</span></b> means 10 Hours and 25 Minutes</p>
</div>
<h2>Showing the Time</h2>
<iframe src="measure/iclock-write.html" scrolling="no" style="width:252px; height:102px; overflow:hidden; margin:auto; display:block; border: none;"></iframe>
<p>There are two main ways to show the time: "24 Hour Clock" or "AM/PM":</p>
<div class="def"><b>24 Hour Clock:</b> the time is shown as how many hours and minutes since midnight.</div>
<div class="def"><b>AM/PM</b> (or "12 Hour Clock"): the day is split into:
<ul style="margin: 10px 0 0 0;">
<li>the 12 Hours running from Midnight to Noon (the <b>AM</b> hours), and</li>
<li>the
other 12 Hours running from Noon to Midnight (the <b>PM</b> hours).</li>
</ul></div>
<p>Like this (try the slider):</p>
<div class="script" style="height: 120px;">
measure/images/time-am-pm.js
</div>
<p class="center"><img src="measure/images/day-am-pm.svg" alt="day am pm" height="204" width="535"></p>
<div class="simple">
<table align="center" cellpadding="3" border="0">
<tbody>
<tr>
<th style="width:190px;">
<div class="center"><b>AM</b></div> </th>
<th style="width:190px;">
<div class="center"><b>PM</b></div> </th>
</tr>
<tr>
<td>
<div class="center"><b>A</b>nte <b>M</b>eridiem*<br>
<i>Latin for "before midday"</i></div> </td>
<td>
<div class="center"><b>P</b>ost <b>M</b>eridiem*<br>
<i>Latin for "after midday"</i></div> </td>
</tr>
<tr>
<td>
<div class="center">Midnight to Noon</div> </td>
<td>
<div class="center">Noon to Midnight</div> </td>
</tr>
<tr>
<td>
<div class="center large">24 Hour:<br>00:00 to 11:59</div> </td>
<td>
<div class="center large">24 Hour:<br>12:00 to 23:59</div> </td>
</tr>
</tbody></table>
</div>
<p class="center"><i>*Is that spelled "Meridiem" or "Meridian"? See <a href="#meridiem">here</a>.</i></p>
<h2>Converting AM/PM to 24 Hour Clock</h2>
<p><b>Add 12 to any hour after Noon</b> (and subtract 12 for the first hour of the day):</p>
<p class="dotpoint">For the first hour of the day (12 Midnight to 12:59 AM), subtract 12 Hours</p>
<div class="so">Examples: 12 Midnight = 00:00, 12:35 AM = 00:35</div>
<p class="dotpoint">From 1:00 AM to 12:59 PM, no change</p>
<div class="so">Examples: 11:20 AM = 11:20, 12:30 PM = 12:30</div>
<p class="dotpoint">From 1:00 PM to 11:59 PM, add 12 Hours</p>
<div class="so">Examples: 4:45 PM = 16:45, 11:50 PM = 23:50</div><br>
<h2>Converting 24 Hour Clock to AM/PM</h2>
<p class="dotpoint">For the first hour of the day (00:00 to 00:59), add 12 Hours, make it "AM"</p>
<div class="so">Examples: 00:10 = 12:10 AM, 00:40 = 12:40 AM</div>
<p class="dotpoint">From 01:00 to 11:59, just make it "AM"</p>
<div class="so">Examples: 01:15 = 1:15 AM, 11:25 = 11:25 AM</div>
<p class="dotpoint">From 12:00 to 12:59, just make it "PM"</p>
<div class="so">Examples: 12:10 = 12:10 PM, 12:55 = 12:55 PM</div>
<p class="dotpoint">From 13:00 to 23:59, subtract 12 Hours, make it "PM"</p>
<div class="so">Examples: 14:55 = 2:55 PM, 23:30 = 11:30 PM</div>
<p>&nbsp;</p>
<h2>Comparison Chart</h2>
<p>
Here is a side-by-side comparison of the 24 Hour Clock and AM/PM: </p>
<table style="border: 0; margin:auto; color:black;">
<tbody>
<tr style="text-align:right;">
<td colspan="2" bgcolor="#FFFFCC">
<div class="center"></div>
<div class="center"><b>Example: on the hour</b></div> </td>
<td><br>
</td>
<td colspan="2" bgcolor="#FFFFCC">
<div class="center"><b>Example: 10 minutes past</b></div> </td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#FFFFCC">
<div class="center"><b>24 Hour Clock</b></div> </td>
<td bgcolor="#FFFFCC"> <b>AM / PM</b></td>
<td><br>
</td>
<td bgcolor="#FFFFCC">
<div class="center"><b>24 Hour Clock</b></div> </td>
<td bgcolor="#FFFFCC"> <b>AM / PM</b></td>
</tr>
<tr style="text-align:right;">
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
<td>&nbsp;</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#5577BB"><b>00:00</b></td>
<td bgcolor="#5577BB"><b>12 Midnight</b></td>
<td><br>
</td>
<td bgcolor="#5577BB"><b>00:10</b></td>
<td bgcolor="#5577BB"><b>12:10 AM</b></td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#5577BB">01:00</td>
<td bgcolor="#5577BB">1:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#5577BB">01:10</td>
<td bgcolor="#5577BB">1:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#6688BB">02:00</td>
<td bgcolor="#6688BB">2:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#6688BB">02:10</td>
<td bgcolor="#6688BB">2:10 AM</td>
</tr>
<tr style="text-align:right;">
<td height="14" bgcolor="#7788BB">03:00</td>
<td height="14" bgcolor="#7788BB">3:00 AM</td>
<td height="14">&nbsp;</td>
<td height="14" bgcolor="#7788BB">03:10</td>
<td height="14" bgcolor="#7788BB">3:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#8899BB">04:00</td>
<td bgcolor="#8899BB">4:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#8899BB">04:10</td>
<td bgcolor="#8899BB">4:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#99AABB">05:00</td>
<td bgcolor="#99AABB">5:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#99AABB">05:10</td>
<td bgcolor="#99AABB">5:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#AABBCC">06:00</td>
<td bgcolor="#AABBCC">6:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#AABBCC">06:10</td>
<td bgcolor="#AABBCC">6:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#AABBCC">07:00</td>
<td bgcolor="#AABBCC">7:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#AABBCC">07:10</td>
<td bgcolor="#AABBCC">7:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#BBCCCC">08:00</td>
<td bgcolor="#BBCCCC">8:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#BBCCCC">08:10</td>
<td bgcolor="#BBCCCC">8:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#CCDDCC">09:00</td>
<td bgcolor="#CCDDCC">9:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#CCDDCC">09:10</td>
<td bgcolor="#CCDDCC">9:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#DDEECC">10:00</td>
<td bgcolor="#DDEECC">10:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#DDEECC">10:10</td>
<td bgcolor="#DDEECC">10:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#EEEECC">11:00</td>
<td bgcolor="#EEEECC">11:00 AM</td>
<td>&nbsp;</td>
<td bgcolor="#EEEECC">11:10</td>
<td bgcolor="#EEEECC">11:10 AM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#FFFFCC"><b>12:00</b></td>
<td bgcolor="#FFFFCC"><b>12 Noon</b></td>
<td>&nbsp;</td>
<td bgcolor="#FFFFCC"><b>12:10</b></td>
<td bgcolor="#FFFFCC"><b>12:10 PM</b></td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#EEEECC">13:00</td>
<td bgcolor="#EEEECC">1:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#EEEECC">13:10</td>
<td bgcolor="#EEEECC">1:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#DDEECC">14:00</td>
<td bgcolor="#DDEECC">2:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#DDEECC">14:10</td>
<td bgcolor="#DDEECC">2:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#CCDDCC">15:00</td>
<td bgcolor="#CCDDCC">3:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#CCDDCC">15:10</td>
<td bgcolor="#CCDDCC">3:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#BBCCCC">16:00</td>
<td bgcolor="#BBCCCC">4:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#BBCCCC">16:10</td>
<td bgcolor="#BBCCCC">4:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#AABBCC">17:00</td>
<td bgcolor="#AABBCC">5:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#AABBCC">17:10</td>
<td bgcolor="#AABBCC">5:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#AABBCC">18:00</td>
<td bgcolor="#AABBCC">6:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#AABBCC">18:10</td>
<td bgcolor="#AABBCC">6:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#99AABB">19:00</td>
<td bgcolor="#99AABB">7:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#99AABB">19:10</td>
<td bgcolor="#99AABB">7:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#8899BB">20:00</td>
<td bgcolor="#8899BB">8:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#8899BB">20:10</td>
<td bgcolor="#8899BB">8:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#7788BB">21:00</td>
<td bgcolor="#7788BB">9:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#7788BB">21:10</td>
<td bgcolor="#7788BB">9:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#6688BB">22:00</td>
<td bgcolor="#6688BB">10:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#6688BB">22:10</td>
<td bgcolor="#6688BB">10:10 PM</td>
</tr>
<tr style="text-align:right;">
<td bgcolor="#5577BB">23:00</td>
<td bgcolor="#5577BB">11:00 PM</td>
<td>&nbsp;</td>
<td bgcolor="#5577BB">23:10</td>
<td bgcolor="#5577BB">11:10 PM</td>
</tr>
</tbody></table>
<h2>Midnight and Noon</h2>
<p>"12 AM" and "12 PM" can cause confusion, so we prefer "12 Midnight" and "12
Noon".</p>
<h2>What Day is Midnight?</h2>
<p>Midnight has another problem: there is nothing to tell us "is this the beginning or ending of the day".</p>
<div class="example">
<p style="float:right; margin: 0 0 5px 10px;"><img src="images/holiday.jpg" alt="holiday" height="180" width="120"></p>
<p>Imagine your friends say they are leaving for holiday at "midnight" on 12th March, what day should you arrive to say goodbye?</p>
<p>Do you get there on the 11th (assuming they leave at the very start of the 12th), or the 12th (assuming they leave at the end of the 12th)?</p>
<div class="indent50px">
<p>It is better to use:</p>
<ul>
<li>11:59 PM or 12:01 AM, or</li>
<li>23:59 or 00:01 (24-Hour Clock)</li>
</ul>
<p>which the railroads, airlines and military actually do.</p>
</div>
</div>
<p>So, when you see something like "offer ends midnight October 15th" tell them to use one minute before or after so there is no confusion!</p>
<p>&nbsp;</p>
<div class="simple">
<div class="words">
<h3><a name="meridiem" id="meridiem"></a>Footnote on "Meridiem" vs "Meridian"</h3>
<p>Should "AM" be "ante meridi<b>em</b>" or "ante meridi<b>an</b>" (likewise for PM)?</p>
<p>The official (according to an American, Australian and British dictionary), and most common, spelling for AM is "ante <b>meridiem</b>" which is a Latin phrase. I recommend that spelling!</p>
<p>But people <i>sometimes</i> use the phrase "ante meridian" (a "meridian" in this case refers to an imaginary line in the sky when the sun is at its highest point).</p>
</div>
</div>
<p>&nbsp;</p>
<div class="questions">3698, 3699, 3700, 3701, 3702, 3703, 3704, 3705, 3658, 3660</div>
<div class="related">
<a href="time-add-subtract.html">Adding and Subtracting Time</a>
<a href="time-clocks.html">Clocks - Digital and Analog</a>
<a href="sun-clock.html">Sun Clock</a>
<a href="time-zones-world.html">World Time Zones</a>
<a href="earth-orbit.html">Earth's Orbit and Daylight</a>
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