Corrected timezone handling for recurring events

ical.js

@@ -156,9 +156,19 @@ function getTimeZone(value) {
   // And offset is still present
   if (tz && tz.startsWith('(')) {
     // Extract just the offset
-    const regex = /[+|-]\d*:\d*/;
+    const offsetcomps = tz.match(/([+|-]\d+):?(\d+)/);
+    if (offsetcomps && offsetcomps[0]) {
+      if (offsetcomps[3] && offsetcomps[3] !== '00') {
+        // Unpack sub-hour offsets, even if they cannot be mapped
+        found = String(offsetcomps[0]);
+      } else {
+        // Map full-hour offsets to IANA Etc zones
+        const intoffset = -1 * Number.parseInt(offsetcomps[1], 10);
+        found = 'Etc/GMT' + (intoffset < 0 ? '' : '+') + intoffset;
+      }
+    }
+
     tz = null;
-    found = tz.match(regex);
   }
 
   // Timezone not confirmed yet
@@ -251,22 +261,27 @@ const dateParameter = function (name) {
           const tz1 = getTimeZone(tz);
           if (tz1) {
             tz = tz1;
-            // We have a confirmed timezone, don't use offset, may confuse DST/STD time
-            offset = '';
             // Fix the parameters for later use
             parameters[0] = 'TZID=' + tz;
           }
         }
 
         // Watch out for offset timezones
         // If the conversion above didn't find any matching IANA tz
-        // And offset is still present
         if (tz && tz.startsWith('(')) {
           // Extract just the offset
-          const regex = /[+|-]\d*:\d*/;
-          offset = tz.match(regex);
+          const offsetcomps = tz.match(/([+|-]\d+):?(\d+)/);
+          if (offsetcomps && offsetcomps[0]) {
+            if (offsetcomps[3] && offsetcomps[3] !== '00') {
+              offset = String(offsetcomps[0]);
+              found = offset;
+            } else {
+              const intoffset = -1 * Number.parseInt(offsetcomps[1], 10);
+              found = 'Etc/GMT' + (intoffset < 0 ? '' : '+') + intoffset;
+            }
+          }
+
           tz = null;
-          found = offset;
         }
 
         // Timezone not confirmed yet
@@ -278,7 +293,7 @@ const dateParameter = function (name) {
         }
 
         // Timezone confirmed or forced to offset
-        newDate = found ? moment.tz(value, 'YYYYMMDDTHHmmss' + offset, tz).toDate() : new Date(
+        newDate = found ? moment.tz(value, 'YYYYMMDDTHHmmss' + offset, found).toDate() : new Date(
           Number.parseInt(comps[1], 10),
           Number.parseInt(comps[2], 10) - 1,
           Number.parseInt(comps[3], 10),
@@ -576,7 +591,6 @@ module.exports = {
       // Recurrence rules are only valid for VEVENT, VTODO, and VJOURNAL.
       // More specifically, we need to filter the VCALENDAR type because we might end up with a defined rrule
       // due to the subtypes.
-
       if ((value === 'VEVENT' || value === 'VTODO' || value === 'VJOURNAL') && curr.rrule) {
         let rule = curr.rrule.replace('RRULE:', '');
         // Make sure the rrule starts with FREQ=
@@ -613,7 +627,9 @@ module.exports = {
               // If the original date has a TZID, add it
               if (curr.start.tz) {
                 const tz = getTimeZone(curr.start.tz);
-                rule += `;DTSTART;TZID=${tz}:${curr.start.toISOString().replace(/[-:]/g, '')}`;
+                const tzoffset = moment.tz(tz).utcOffset() * -60000;
+                const localISOTime = (new Date(curr.start - tzoffset)).toISOString().slice(0, -1);
+                rule += `;DTSTART;TZID=${tz}:${localISOTime.replace(/[-:]/g, '')}`;
               } else {
                 rule += `;DTSTART=${curr.start.toISOString().replace(/[-:]/g, '')}`;
               }

test/test.js

@@ -150,8 +150,10 @@ vows
           });
         },
         'tzid offset correctly applied'(event) {
-          const start = new Date('2002-10-28T22:00:00.000Z');
-          assert.equal(event.start.valueOf(), start.valueOf());
+          assert.ok(moment.tz.zone(event.start.tz), 'zone does not exist');
+          const ref = '2002-10-28T22:00:00Z';
+          const start = moment(event.start).tz(event.start.tz);
+          assert.equal(start.utc().format(), ref);
         }
       }
     },
@@ -1038,6 +1040,84 @@ vows
           assert.equal(event.end.toDateString(), new Date(2024, 1, 22).toDateString());
         }
       }
+    },
+    'with test22.ics (testing dtstart of rrule with timezones)': {
+      topic() {
+        return ical.parseFile('./test/test22.ics');
+      },
+      'first event': {
+        topic(events) {
+          return _.select(_.values(events), x => {
+            return x.uid === '000021a';
+          })[0];
+        },
+        'datetype is date-time'(topic) {
+          assert.equal(topic.datetype, 'date-time');
+        },
+        'has GMT+1 timezone'(topic) {
+          assert.equal(topic.start.tz, 'Europe/Berlin');
+        },
+        'starts 14 Jul 2022 @ 12:00:00 (UTC)'(topic) {
+          assert.equal(topic.start.toISOString(), '2022-07-14T12:00:00.000Z');
+        }
+      },
+      'recurring yearly frist event (14 july)': {
+        topic(events) {
+          const ev = _.select(_.values(events), x => {
+            return x.uid === '000021a';
+          })[0];
+          return ev.rrule.between(new Date(2023, 0, 1), new Date(2024, 0, 1))[0];
+        },
+        'dt start well set'(topic) {
+          assert.equal(topic.toDateString(), new Date(2023, 6, 14).toDateString());
+        },
+        'starts 14 Jul 2023 @ 12:00:00 (UTC)'(topic) {
+          assert.equal(topic.toISOString(), '2023-07-14T12:00:00.000Z');
+        }
+      },
+      'second event': {
+        topic(events) {
+          return _.select(_.values(events), x => {
+            return x.uid === '000021b';
+          })[0];
+        },
+        'datetype is date-time'(event) {
+          assert.equal(event.datetype, 'date-time');
+        },
+        'start date': {
+          topic(event) {
+            return event.start;
+          },
+          'has correct timezone'(start) {
+            assert.equal(start.tz, '(GMT +02:00)');
+          },
+          'starts 15 Jul 2022 @ 12:00:00 (UTC)'(start) {
+            assert.equal(start.toISOString(), '2022-07-15T12:00:00.000Z');
+          }
+        },
+        'has recurrences': {
+          topic(event) {
+            return event.rrule;
+          },
+          'that are defined'(rrule) {
+            assert.ok(rrule, 'no rrule defined');
+          },
+          'that have timezone info'(rrule) {
+            assert.ok(rrule.options.tzid, 'no tzid property on rrule');
+          },
+          'that keep correct timezone info in recurrences'(rrule) {
+            assert.equal(rrule.options.tzid, 'Etc/GMT-2');
+          }
+        },
+        'has a first recurrence': {
+          topic(event) {
+            return event.rrule.between(new Date(2023, 0, 1), new Date(2024, 0, 1))[0];
+          },
+          'that starts 15 Jul 2023 @ 12:00:00 (UTC)'(rc) {
+            assert.equal(rc.toISOString(), '2023-07-15T12:00:00.000Z');
+          }
+        }
+      }
     }
   })
   .export(module);

test/test21-mod.ics

@@ -0,0 +1,21 @@
+BEGIN:VCALENDAR
+BEGIN:VEVENT
+TRANSP:OPAQUE
+X-MICROSOFT-CDO-INTENDEDSTATUS:BUSY
+CREATED:20221004T073016Z
+LAST-MODIFIED:20221011T063437Z
+DTSTAMP:20221011T063437Z
+DTSTART;TZID="(GMT +01:00)":20221004T140000
+DTEND;TZID="(GMT +01:00)":20221004T150000
+SUMMARY:Music School 
+CLASS:PUBLIC
+UID:0000021
+X-MOZ-SNOOZE-TIME:20221004T113000Z
+X-MICROSOFT-CDO-OWNER-CRITICAL-CHANGE:20221014T203413Z
+X-MICROSOFT-CDO-ATTENDEE-CRITICAL-CHANGE:20221014T203413Z
+X-MICROSOFT-CDO-APPT-SEQUENCE:0
+X-MICROSOFT-CDO-OWNERAPPTID:-1
+X-MICROSOFT-CDO-ALLDAYEVENT:FALSE
+RRULE:FREQ=WEEKLY;UNTIL=20221201T020000;BYDAY=TU
+END:VEVENT
+END:VCALENDAR

test/test22.ics

@@ -0,0 +1,26 @@
+BEGIN:VCALENDAR
+VERSION:2.0
+PRODID:Fictitious Recurrence Test Calendar
+BEGIN:VEVENT
+CREATED:20221018T221500Z
+DTSTAMP:20221019T171200Z
+UID:000021a
+SUMMARY:Party
+RRULE:FREQ=YEARLY
+DTSTART;TZID=Europe/Berlin:20220714T140000
+DTEND;TZID=Europe/Berlin:20220714T210000
+TRANSP:OPAQUE
+SEQUENCE:5
+END:VEVENT
+BEGIN:VEVENT
+CREATED:20221019T181700Z
+DTSTAMP:20221019T191200Z
+UID:000021b
+SUMMARY:Party next day
+RRULE:FREQ=YEARLY
+DTSTART;TZID="(GMT +02:00)":20220715T140000
+DTEND;TZID="(GMT +02:00)":20220715T210000
+TRANSP:OPAQUE
+SEQUENCE:5
+END:VEVENT
+END:VCALENDAR