diff --git a/API.txt b/API.txt
index 65400c6..daf2317 100644
--- a/API.txt
+++ b/API.txt
@@ -501,6 +501,7 @@ through the following axis options:
   minTickSize: array
   timeformat: null or format string
   monthNames: null or array of size 12 of strings
+  dayNames: null or array of size 7 of strings
   twelveHourClock: boolean
 
 Here "timeformat" is a format string to use. You might use it like
@@ -508,41 +509,47 @@ this:
 
   xaxis: {
     mode: "time"
-    timeformat: "%y/%m/%d"
+    timeformat: "%Y/%m/%d"
   }
   
-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), use %0d for zero-padding
-  %m: month (1-12), use %0m for zero-padding
-  %y: year (four digits)
+This will result in tick labels like "2000/12/24". A subset of the 
+standard strftime specifiers are supported:
+
+  %a: weekday name (customizable)
   %b: month name (customizable)
-  %p: am/pm, additionally switches %h/%H to 12 hour instead of 24
+  %d: day of month, zero-padded (01-31)
+  %e: day of month, space-padded ( 1-31)
+  %H: hours, 24-hour time, zero-padded (00-23)
+  %I: hours, 12-hour time, zero-padded (01-12)
+  %m: month, zero-padded (01-12)
+  %M: minutes, zero-padded (00-59)
+  %S: seconds, zero-padded (00-59)
+  %y: year (two digits)
+  %Y: year (four digits)
+  %p: am/pm
   %P: AM/PM (uppercase version of %p)
-
-Inserting a zero like %0m or %0d means that the specifier will be
-left-padded with a zero if it's only single-digit. So %y-%0m-%0d
-results in unambigious ISO timestamps like 2007-05-10 (for May 10th).
+  %w: weekday as number (0-6, 0 being Sunday)
 
 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"]
 
+Similarly you can customize the weekday names with the "dayNames"
+option. An example in French:
+
+  dayNames: ["dim", "lun", "mar", "mer", "jeu", "ven", "sam"]
+
 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.
-If needed, you can access it as $.plot.formatDate(date, formatstring,
-monthNames) or even replace it with another more advanced function
-from a date library if you're feeling adventurous.
+will use 12 hour AM/PM timestamps instead of 24 hour. This only
+applies if you have not set "timeformat". Use the "%I" and "%p" or
+"%P" options if you want to build your own format string with 12-hour
+times.
+
+If the Date object has a strftime property (and it is a function), it
+will be used instead of the built-in formatter. Thus you can include
+a strftime library such as http://hacks.bluesmoon.info/strftime/ for
+more powerful date/time formatting.
 
 If everything else fails, you can control the formatting by specifying
 a custom tick formatter function as usual. Here's a simple example
diff --git a/NEWS.txt b/NEWS.txt
index 6175ca3..d00b210 100644
--- a/NEWS.txt
+++ b/NEWS.txt
@@ -15,6 +15,11 @@ control how the dates are displayed. If null, the dates are displayed
 as UTC. If "browser", the dates are displayed in the time zone of the
 user's browser.
 
+Date/time formatting has changed and now follows a proper subset
+of the standard strftime specifiers. Additionally, if a strftime
+function is found in the Date object's prototype, it will be used
+instead of the built-in formatter.
+
 Axis labels are now drawn with canvas text with some parsing to
 support newlines. This solves various issues but also means that they
 no longer support HTML markup, can be accessed as DOM elements or
@@ -29,6 +34,10 @@ and "flot-overlay" to prevent accidental clashes (issue 540).
 
 Changes:
 
+- Date/time formatting follows proper subset of strftime specifiers,
+  and support added for Date.prototype.strftime, if found (patch by
+  Mark Cote, issue 558).
+
 - Fixed display of year ticks (patch by Mark Cote, issue 195).
 
 - Support for time series moved to plugin (patch by Mark Cote).
diff --git a/examples/time.html b/examples/time.html
index 4a6e908..8eb1c0b 100644
--- a/examples/time.html
+++ b/examples/time.html
@@ -23,7 +23,9 @@
     <p>Zoom to: <button id="whole">Whole period</button>
       <button id="nineties">1990-2000</button>
       <button id="latenineties">1996-2000</button>
-      <button id="ninetynine">1999</button></p>
+      <button id="ninetynine">1999</button>
+      <button id="lastweekninetynine">end of 1999</button>
+      <button id="lastdayninetynine">very end of 1999</button></p>
 
     <p>The timestamps must be specified as Javascript timestamps, as
       milliseconds since January 1, 1970 00:00. This is like Unix
@@ -31,10 +33,10 @@
       multiply with 1000!).</p>
 
     <p>As an extra caveat, the timestamps are interpreted according to
-      UTC to avoid having the graph shift with each visitor's local
-      time zone. So you might have to add your local time zone offset
-      to the timestamps or simply pretend that the data was produced
-      in UTC instead of your local time zone.</p>
+      UTC and, by default, displayed as such. You can set the axis
+      "timezone" option to "browser" to display the timestamps in the
+      user's timezone, or, if you use timezoneJS, you can specify a
+      time zone.</p>
 
 <script id="source">
 $(function () {
@@ -50,8 +52,8 @@ $(function () {
         $.plot($("#placeholder"), [d], {
             xaxis: {
                 mode: "time",
-                min: (new Date(1990, 1, 1)).getTime(),
-                max: (new Date(2000, 1, 1)).getTime()
+                min: (new Date(1990, 0, 1)).getTime(),
+                max: (new Date(2000, 0, 1)).getTime()
             }
         });
     });
@@ -61,8 +63,8 @@ $(function () {
             xaxis: {
                 mode: "time",
                 minTickSize: [1, "year"],
-                min: (new Date(1996, 1, 1)).getTime(),
-                max: (new Date(2000, 1, 1)).getTime()
+                min: (new Date(1996, 0, 1)).getTime(),
+                max: (new Date(2000, 0, 1)).getTime()
             }
         });
     });
@@ -72,8 +74,32 @@ $(function () {
             xaxis: {
                 mode: "time",
                 minTickSize: [1, "month"],
-                min: (new Date(1999, 1, 1)).getTime(),
-                max: (new Date(2000, 1, 1)).getTime()
+                min: (new Date(1999, 0, 1)).getTime(),
+                max: (new Date(2000, 0, 1)).getTime()
+            }
+        });
+    });
+
+    $("#lastweekninetynine").click(function () {
+        $.plot($("#placeholder"), [d], {
+            xaxis: {
+                mode: "time",
+                minTickSize: [1, "day"],
+                min: (new Date(1999, 11, 25)).getTime(),
+                max: (new Date(2000, 0, 1)).getTime(),
+                timeformat: "%a"
+            }
+        });
+    });
+
+    $("#lastdayninetynine").click(function () {
+        $.plot($("#placeholder"), [d], {
+            xaxis: {
+                mode: "time",
+                minTickSize: [1, "hour"],
+                min: (new Date(1999, 11, 31)).getTime(),
+                max: (new Date(2000, 0, 1)).getTime(),
+                twelveHourClock: true
             }
         });
     });
diff --git a/jquery.flot.time.js b/jquery.flot.time.js
index 508be90..dfe7244 100644
--- a/jquery.flot.time.js
+++ b/jquery.flot.time.js
@@ -12,51 +12,59 @@ for details.
         return base * Math.floor(n / base);
     }
 
-    // returns a string with the date d formatted according to fmt
-    function formatDate(d, fmt, monthNames) {
-        var leftPad = function(n) {
+    // Returns a string with the date d formatted according to fmt.
+    // A subset of the Open Group's strftime format is supported.
+    function formatDate(d, fmt, monthNames, dayNames) {
+        if (typeof d.strftime == "function") {
+            return d.strftime(fmt);
+        }
+        var leftPad = function(n, pad) {
             n = "" + n;
-            return n.length == 1 ? "0" + n : n;
+            pad = "" + (pad == null ? "0" : pad);
+            return n.length == 1 ? pad + n : n;
         };
         
         var r = [];
-        var escape = false, padNext = false;
+        var escape = false;
         var hours = d.getHours();
         var isAM = hours < 12;
         if (monthNames == null)
             monthNames = ["Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"];
+        if (dayNames == null)
+            dayNames = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"];
 
-        if (fmt.search(/%p|%P/) != -1) {
-            if (hours > 12) {
-                hours = hours - 12;
-            } else if (hours == 0) {
-                hours = 12;
-            }
+        var hours12;
+        if (hours > 12) {
+            hours12 = hours - 12;
+        } else if (hours == 0) {
+            hours12 = 12;
+        } else {
+            hours12 = hours;
         }
+
         for (var i = 0; i < fmt.length; ++i) {
             var c = fmt.charAt(i);
             
             if (escape) {
                 switch (c) {
-                case 'h': c = "" + hours; break;
+                case 'a': c = "" + dayNames[d.getDay()]; break;
+                case 'b': c = "" + monthNames[d.getMonth()]; break;
+                case 'd': c = leftPad(d.getDate()); break;
+                case 'e': c = leftPad(d.getDate(), " "); break;
                 case 'H': c = leftPad(hours); break;
+                case 'I': c = leftPad(hours12); break;
+                case 'l': c = leftPad(hours12, " "); break;
+                case 'm': c = leftPad(d.getMonth() + 1); break;
                 case 'M': c = leftPad(d.getMinutes()); break;
                 case 'S': c = leftPad(d.getSeconds()); break;
-                case 'd': c = "" + d.getDate(); break;
-                case 'm': c = "" + (d.getMonth() + 1); break;
-                case 'y': c = "" + d.getFullYear(); break;
-                case 'b': c = "" + monthNames[d.getMonth()]; break;
+                case 'y': c = leftPad(d.getFullYear() % 100); break;
+                case 'Y': c = "" + d.getFullYear(); break;
                 case 'p': c = (isAM) ? ("" + "am") : ("" + "pm"); break;
                 case 'P': c = (isAM) ? ("" + "AM") : ("" + "PM"); break;
-                case '0': c = ""; padNext = true; break;
-                }
-                if (c && padNext) {
-                    c = leftPad(c);
-                    padNext = false;
+                case 'w': c = "" + d.getDay(); break;
                 }
                 r.push(c);
-                if (!padNext)
-                    escape = false;
+                escape = false;
             }
             else {
                 if (c == "%")
@@ -77,11 +85,14 @@ for details.
                                 targetMethod) {
             sourceObj[sourceMethod] = function() {
                 return targetObj[targetMethod].apply(targetObj, arguments);
-            }
+            };
         };
         var utc = {
             date: d
         };
+        // support strftime, if found
+        if (d.strftime != undefined)
+            addProxyMethod(utc, "strftime", d, "strftime");
         addProxyMethod(utc, "getTime", d, "getTime");
         addProxyMethod(utc, "setTime", d, "setTime");
         var props = [ "Date", "Day", "FullYear", "Hours", "Milliseconds", "Minutes", "Month", "Seconds" ];
@@ -254,19 +265,20 @@ for details.
 
                         // first check global format
                         if (opts.timeformat != null)
-                            return formatDate(d, opts.timeformat, opts.monthNames);
+                            return formatDate(d, opts.timeformat, opts.monthNames, opts.dayNames);
                         
                         var t = axis.tickSize[0] * timeUnitSize[axis.tickSize[1]];
                         var span = axis.max - axis.min;
                         var suffix = (opts.twelveHourClock) ? " %p" : "";
+                        var hourCode = (opts.twelveHourClock) ? "%I" : "%H";
                         
                         if (t < timeUnitSize.minute)
-                            fmt = "%h:%M:%S" + suffix;
+                            fmt = hourCode + ":%M:%S" + suffix;
                         else if (t < timeUnitSize.day) {
                             if (span < 2 * timeUnitSize.day)
-                                fmt = "%h:%M" + suffix;
+                                fmt = hourCode + ":%M" + suffix;
                             else
-                                fmt = "%b %d %h:%M" + suffix;
+                                fmt = "%b %d " + hourCode + ":%M" + suffix;
                         }
                         else if (t < timeUnitSize.month)
                             fmt = "%b %d";
@@ -274,12 +286,12 @@ for details.
                             if (span < timeUnitSize.year)
                                 fmt = "%b";
                             else
-                                fmt = "%b %y";
+                                fmt = "%b %Y";
                         }
                         else
-                            fmt = "%y";
+                            fmt = "%Y";
                         
-                        var rt = formatDate(d, fmt, opts.monthNames);
+                        var rt = formatDate(d, fmt, opts.monthNames, opts.dayNames);
                         return rt;
                     };
                 }