diff --git a/lib/index.js b/lib/index.js
index d448d8d..fc1f3ba 100644
--- a/lib/index.js
+++ b/lib/index.js
@@ -70,45 +70,68 @@
       d = new Date(d.getTime() + msDelta);
     }
 
-    // Most of the specifiers supported by C's strftime, and one from Ruby (%L)
-    return fmt.replace(/%(.)/g, function(_, c) {
+    // Most of the specifiers supported by C's strftime, and some from Ruby.
+    // Some other syntax extensions from Ruby are supported: %-, %_, and %0
+    // to pad with nothing, space, or zero (respectively).
+    return fmt.replace(/%([-_0]?.)/g, function(_, c) {
+      var mod, padding;
+      if (c.length == 2) {
+        mod = c[0];
+        // omit padding
+        if (mod == '-') {
+          padding = '';
+        }
+        // pad with space
+        else if (mod == '_') {
+          padding = ' ';
+        }
+        // pad with zero
+        else if (mod == '0') {
+          padding = '0';
+        }
+        else {
+          // unrecognized, return the format
+          return _;
+        }
+        c = c[1];
+      }
       switch (c) {
         case 'A': return locale.days[d.getDay()];
         case 'a': return locale.shortDays[d.getDay()];
         case 'B': return locale.months[d.getMonth()];
         case 'b': return locale.shortMonths[d.getMonth()];
-        case 'C': return pad(Math.floor(d.getFullYear() / 100));
+        case 'C': return pad(Math.floor(d.getFullYear() / 100), padding);
         case 'D': return _strftime(locale.formats.D || '%m/%d/%y', d, locale);
-        case 'd': return pad(d.getDate());
+        case 'd': return pad(d.getDate(), padding);
         case 'e': return d.getDate();
         case 'F': return _strftime(locale.formats.F || '%Y-%m-%d', d, locale);
-        case 'H': return pad(d.getHours());
+        case 'H': return pad(d.getHours(), padding);
         case 'h': return locale.shortMonths[d.getMonth()];
-        case 'I': return pad(hours12(d));
+        case 'I': return pad(hours12(d), padding);
         case 'j':
           var y=new Date(d.getFullYear(), 0, 1);
           var day = Math.ceil((d.getTime() - y.getTime()) / (1000*60*60*24));
           return day;
-        case 'k': return pad(d.getHours(), ' ');
+        case 'k': return pad(d.getHours(), padding == null ? ' ' : padding);
         case 'L': return pad(Math.floor(d.getTime() % 1000), 3);
-        case 'l': return pad(hours12(d), ' ');
-        case 'M': return pad(d.getMinutes());
-        case 'm': return pad(d.getMonth() + 1);
+        case 'l': return pad(hours12(d), padding == null ? ' ' : padding);
+        case 'M': return pad(d.getMinutes(), padding);
+        case 'm': return pad(d.getMonth() + 1, padding);
         case 'n': return '\n';
         case 'P': return d.getHours() < 12 ? locale.am : locale.pm;
         case 'p': return d.getHours() < 12 ? locale.AM : locale.PM;
         case 'R': return _strftime(locale.formats.R || '%H:%M', d, locale);
         case 'r': return _strftime(locale.formats.r || '%I:%M:%S %p', d, locale);
-        case 'S': return pad(d.getSeconds());
+        case 'S': return pad(d.getSeconds(), padding);
         case 's': return Math.floor((d.getTime() - msDelta) / 1000);
         case 'T': return _strftime(locale.formats.T || '%H:%M:%S', d, locale);
         case 't': return '\t';
-        case 'U': return pad(weekNumber(d, 'sunday'));
+        case 'U': return pad(weekNumber(d, 'sunday'), padding);
         case 'u':
           var day = d.getDay();
           return day == 0 ? 7 : day; // 1 - 7, Monday is first day of the week
         case 'v': return _strftime(locale.formats.v || '%e-%b-%Y', d, locale);
-        case 'W': return pad(weekNumber(d, 'monday'));
+        case 'W': return pad(weekNumber(d, 'monday'), padding);
         case 'w': return d.getDay(); // 0 - 6, Sunday is first day of the week
         case 'Y': return d.getFullYear();
         case 'y':
@@ -157,11 +180,16 @@
     }
 
     // Defaults handle pad(n) and pad(n, <padding>)
-    padding = padding || '0';
+    if (padding == null) {
+      padding = '0';
+    }
     length = length || 2;
 
     var s = String(n);
-    while (s.length < length) s = padding + s;
+    // padding may be an empty string, don't loop forever if it is
+    if (padding) {
+      while (s.length < length) s = padding + s;
+    }
     return s;
   }
 
diff --git a/test/test.js b/test/test.js
index 2f6478f..b2602cc 100755
--- a/test/test.js
+++ b/test/test.js
@@ -60,15 +60,24 @@ assert.format('%b', 'Jun')
 assert.format('%C', '20')
 assert.format('%D', '06/07/11')
 assert.format('%d', '07')
+assert.format('%-d', '7')
+assert.format('%_d', ' 7')
+assert.format('%0d', '07')
 assert.format('%e', '7')
 assert.format('%F', '2011-06-07')
 assert.format('%H', null, '18')
 assert.format('%h', 'Jun')
 assert.format('%I', null, '06')
+assert.format('%-I', null, '6')
+assert.format('%_I', null, ' 6')
+assert.format('%0I', null, '06')
 assert.format('%j', null, '158')
 assert.format('%k', null, '18')
 assert.format('%L', '067')
 assert.format('%l', null, ' 6')
+assert.format('%-l', null, '6')
+assert.format('%_l', null, ' 6')
+assert.format('%0l', null, '06')
 assert.format('%M', null, '51')
 assert.format('%m', '06')
 assert.format('%n', '\n')