Add number of months instead of weeks if they exceed a certain amount

README.md

@@ -104,3 +104,23 @@ main() {
   );
 }
 ```
+
+## Months instead of weeks
+
+If a duration spans more than two months it will be formatted as 'x months' instead of 'y weeks'.
+To override the amount of months use `minNumberMonths`.
+
+```dart
+main() {
+  // => 8 weeks 4 days
+  printDuration(
+    Duration(days: 60)
+  );
+
+  // => 1 month 30 days
+  printDuration(
+    Duration(days: 60),
+    minNumberMonths: 1
+  );
+}
+```

lib/src/duration.dart

@@ -1,3 +1,5 @@
+import 'package:duration/src/time_const.dart';
+
 import 'locale/locale.dart';
 import 'tersity.dart';
 
@@ -35,7 +37,8 @@ String prettyDuration(Duration duration,
     String delimiter,
     String conjunction,
     bool abbreviated = false,
-    bool first = false}) {
+    bool first = false,
+    int minNumberMonths = 2}) {
   if (abbreviated && delimiter == null) {
     delimiter = ', ';
     spacer = '';
@@ -55,14 +58,22 @@ String prettyDuration(Duration duration,
     return sb.toString();
   };
 
-  final int weeks = (duration.inDays / 7).floor();
+  final int months = (duration.inDays / avgDaysPerMonth).floor();
+  int daysCounted = 0;
 
-  if (weeks > 0) {
-    out.add(partFmt(weeks, locale.week));
+  if (months >= minNumberMonths) {
+    out.add(partFmt(months, locale.month));
+    daysCounted = (months * avgDaysPerMonth).floor();
+  } else {
+    final int weeks = (duration.inDays / 7).floor();
+    if (weeks > 0) {
+      out.add(partFmt(weeks, locale.week));
+      daysCounted = weeks * 7;
+    }
   }
 
   if (tersity >= DurationTersity.day) {
-    final int days = duration.inDays - (weeks * 7);
+    final int days = duration.inDays - daysCounted;
     if (days > 0) out.add(partFmt(days, locale.day));
 
     if (tersity >= DurationTersity.hour) {
@@ -126,14 +137,16 @@ String printDuration(Duration duration,
     String spacer,
     String delimiter,
     String conjugation,
-    bool abbreviated = false}) {
+    bool abbreviated = false,
+    int minNumberMonths = 2}) {
   final String fmt = prettyDuration(duration,
       tersity: tersity,
       locale: locale,
       spacer: spacer,
       delimiter: delimiter,
       conjunction: conjugation,
-      abbreviated: abbreviated);
+      abbreviated: abbreviated,
+      minNumberMonths: minNumberMonths);
   print(fmt);
   return fmt;
 }

lib/src/time_const.dart

@@ -36,3 +36,7 @@ Duration hours(int hours) => Duration(hours: hours);
 
 // Creates a [Duration] with given [days]
 Duration days(int days) => Duration(days: days);
+
+// Average number of days per month (365 / 12)
+// Obviously a bit off on leap years.
+const double avgDaysPerMonth = 30.42;

test/pretty_duration_test.dart

@@ -97,6 +97,19 @@ void main() {
         final dur = Duration(days: 14);
         expect(prettyDuration(dur), '2 weeks');
       }
+
+      {
+        final dur = Duration(days: 60);
+        expect(prettyDuration(dur), '8 weeks 4 days');
+      }
+      {
+        final dur = Duration(days: 61);
+        expect(prettyDuration(dur), '2 months 1 day');
+      }
+      {
+        final dur = Duration(days: 60);
+        expect(prettyDuration(dur, minNumberMonths: 1), '1 month 30 days');
+      }
     });
 
     test('Abbreviated', () {
@@ -204,6 +217,16 @@ void main() {
         final dur = Duration(days: 14);
         expect(prettyDuration(dur, abbreviated: true), '2w');
       }
+
+      {
+        final dur = Duration(days: 60);
+        expect(prettyDuration(dur, abbreviated: true), '8w, 4d');
+      }
+
+      {
+        final dur = Duration(days: 61);
+        expect(prettyDuration(dur, abbreviated: true), '2mon, 1d');
+      }
     });
 
     test('Delimiter', () {