diff --git a/API.txt b/API.txt
index e43d92a..aa5bd12 100644
--- a/API.txt
+++ b/API.txt
@@ -309,7 +309,6 @@ an example of a custom formatter:
       return val.toFixed(axis.tickDecimals) + " B";
   }
 
-
 Time series data
 ================
 
@@ -380,6 +379,7 @@ through the following axis options:
   minTickSize: array
   timeformat: null or format string
   monthNames: null or array of size 12 of strings
+  twelveHourClock: boolean
 
 Here "timeformat" is a format string to use. You might use it like
 this:
@@ -392,20 +392,25 @@ this:
 This will result in tick labels like "2000/12/24". The following
 specifiers are supported
 
-  %h': hours
-  %H': hours (left-padded with a zero)
-  %M': minutes (left-padded with a zero)
-  %S': seconds (left-padded with a zero)
-  %d': day of month (1-31)
-  %m': month (1-12)
-  %y': year (four digits)
-  %b': month name (customizable)
+  %h: hours
+  %H: hours (left-padded with a zero)
+  %M: minutes (left-padded with a zero)
+  %S: seconds (left-padded with a zero)
+  %d: day of month (1-31)
+  %m: month (1-12)
+  %y: year (four digits)
+  %b: month name (customizable)
+  %p: am/pm, additionally switches %h/%H to 12 hour instead of 24
+  %P: AM/PM (uppercase version of %p)
 
 You can customize the month names with the "monthNames" option. For
 instance, for Danish you might specify:
 
   monthNames: ["jan", "feb", "mar", "apr", "maj", "jun", "jul", "aug", "sep", "okt", "nov", "dec"]
 
+If you set "twelveHourClock" to true, the autogenerated timestamps
+will use 12 hour AM/PM timestamps instead of 24 hour.
+  
 The format string and month names are used by a very simple built-in
 format function that takes a date object, a format string (and
 optionally an array of month names) and returns the formatted string.
diff --git a/NEWS.txt b/NEWS.txt
index 965062d..343af64 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -113,6 +113,8 @@ Changes:
 
 - Axis transformation support, useful for non-linear plots, e.g. log
   axes and compressed time axes (like omitting weekends).
+
+- Support for twelve-hour date formatting (patch by Forrest Aldridge).
   
 Bug fixes:
 
diff --git a/jquery.flot.js b/jquery.flot.js
index c44c4cb..eef4760 100644
--- a/jquery.flot.js
+++ b/jquery.flot.js
@@ -43,7 +43,8 @@
                     tickSize: null, // number or [number, "unit"]
                     minTickSize: null, // number or [number, "unit"]
                     monthNames: null, // list of names of months
-                    timeformat: null // format string to use
+                    timeformat: null, // format string to use
+                    twelveHourClock: false // 12 or 24 time in time mode
                 },
                 yaxis: {
                     autoscaleMargin: 0.02
@@ -902,14 +903,15 @@
                     
                     var t = axis.tickSize[0] * timeUnitSize[axis.tickSize[1]];
                     var span = axis.max - axis.min;
+                    var suffix = (axisOptions.twelveHourClock) ? " %p" : "";
                     
                     if (t < timeUnitSize.minute)
-                        fmt = "%h:%M:%S";
+                        fmt = "%h:%M:%S" + suffix;
                     else if (t < timeUnitSize.day) {
                         if (span < 2 * timeUnitSize.day)
-                            fmt = "%h:%M";
+                            fmt = "%h:%M" + suffix;
                         else
-                            fmt = "%b %d %h:%M";
+                            fmt = "%b %d %h:%M" + suffix;
                     }
                     else if (t < timeUnitSize.month)
                         fmt = "%b %d";
@@ -2240,21 +2242,33 @@
         
         var r = [];
         var escape = false;
+        var hours = d.getUTCHours();
+        var isAM = hours < 12;
         if (monthNames == null)
             monthNames = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
+
+        if (fmt.search(/%p|%P/) != -1) {
+            if (hours > 12) {
+                hours = hours - 12;
+            } else if (hours == 0) {
+                hours = 12;
+            }
+        }
         for (var i = 0; i < fmt.length; ++i) {
             var c = fmt.charAt(i);
             
             if (escape) {
                 switch (c) {
-                case 'h': c = "" + d.getUTCHours(); break;
-                case 'H': c = leftPad(d.getUTCHours()); break;
+                case 'h': c = "" + hours; break;
+                case 'H': c = leftPad(hours); break;
                 case 'M': c = leftPad(d.getUTCMinutes()); break;
                 case 'S': c = leftPad(d.getUTCSeconds()); break;
                 case 'd': c = "" + d.getUTCDate(); break;
                 case 'm': c = "" + (d.getUTCMonth() + 1); break;
                 case 'y': c = "" + d.getUTCFullYear(); break;
                 case 'b': c = "" + monthNames[d.getUTCMonth()]; break;
+                case 'p': c = (isAM) ? ("" + "am") : ("" + "pm"); break;
+                case 'P': c = (isAM) ? ("" + "AM") : ("" + "PM"); break;
                 }
                 r.push(c);
                 escape = false;