Automatic computation of easter and related holidays for the calendar

ChangeLog

@@ -2,16 +2,20 @@
 ------ current release ---------------------------
 
 1.9.1 ()
- + Fixed bug #382 in which the annotate command didn't return an error
-   message when called without an ID.
  + Summary report bar colors can now be specified with color.summary.bar
    and color.summary.background configuration variables.
- + The configure script is more portable (thanks to Emil Sköldberg).
- + Updated task-faq.5 man page.
  + The 'edit' command now conveniently fills in the current date for new
    annotations.
  + Deleting a task no longer clobbers any recorded end date (thanks to
    Seneca Cunningham).
+ + Following holidays are now computed automatically:
+   Good Friday (goodfriday), Easter (easter), Easter monday (eastermonday),
+   Ascension (ascension), Pentecost (pentecost)
+   The date is configured with the given keyword.
+ + The configure script is more portable (thanks to Emil Sköldberg).
+ + Updated task-faq.5 man page.
+ + Fixed bug #382 in which the annotate command didn't return an error
+   message when called without an ID.
  + Fixed bug #402 which failed compilation on Arch Linux (thanks to
    Johannes Schlatow).
 

doc/man/taskrc.5

@@ -414,6 +414,19 @@ Dates are to be entered according to the setting in the dateformat.holiday
 variable.
 .RE
 
+.RS
+The following holidays are computed automatically: Good Friday (goodfriday), Easter (easter), Easter monday (eastermonday), Ascension (ascension), Pentecost (pentecost). The date for these holidays is the given keyword:
+.RE
+
+.RS
+.RS
+.br
+holiday.eastersunday.name=Easter
+.br
+holiday.eastersunday.date=easter
+.RE
+.RE
+
 .TP
 .B monthsperline=3
 Determines how many months the "task calendar" command renders across the

src/Date.cpp

@@ -792,7 +792,7 @@ bool Date::sameYear (const Date& rhs)
 ////////////////////////////////////////////////////////////////////////////////
 Date Date::operator+ (const int delta)
 {
-  return Date (mT + delta);
+  return Date::Date (mT + delta);
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -862,6 +862,13 @@ bool Date::isRelativeDate (const std::string& input)
   supported.push_back ("eow");
   supported.push_back ("eom");
   supported.push_back ("eoy");
+  supported.push_back ("goodfriday");
+  supported.push_back ("easter");
+  supported.push_back ("eastermonday");
+  supported.push_back ("ascension");
+  supported.push_back ("pentecost");
+  supported.push_back ("midsommar");
+  supported.push_back ("midsommarafton");
 
   std::vector <std::string> matches;
   if (autoComplete (in, supported, matches) == 1)
@@ -926,6 +933,60 @@ bool Date::isRelativeDate (const std::string& input)
       mT = then.mT;
       return true;
     }
+    else if (found == "goodfriday")
+    {
+      Date then (Date::easter(today.year()));
+      mT = then.mT - 86400*2;
+      return true;
+    }
+    else if (found == "easter")
+    {
+      Date then (Date::easter(today.year()));
+      mT = then.mT;
+      return true;
+    }
+    else if (found == "eastermonday")
+    {
+      Date then (Date::easter(today.year()));
+      mT = then.mT + 86400;
+      return true;
+    }
+    else if (found == "ascension")
+    {
+      Date then (Date::easter(today.year()));
+      mT = then.mT + 86400*39;
+      return true;
+    }
+    else if (found == "pentecost")
+    {
+      Date then (Date::easter(today.year()));
+      mT = then.mT + 86400*49;
+      return true;
+    }
+    else if (found == "midsommar")
+    {
+      for (int midsommar = 20; midsommar <= 26; midsommar++)
+      {
+        Date then (6, midsommar, today.year ());
+        if (6 == then.dayOfWeek ())
+        {
+          mT = then.mT;
+          return true;
+        }
+      }
+    }
+    else if (found == "midsommarafton")
+    {
+      for (int midsommar = 19; midsommar <= 25; midsommar++)
+      {
+        Date then (6, midsommar, today.year ());
+        if (5 == then.dayOfWeek ())
+        {
+          mT = then.mT;
+          return true;
+        }
+      }
+    }
   }
 
   // Support "21st" to indicate the next date that is the 21st day.