Replace hardcoded maxCalendarYear with dynamic config

service/worker/scheduler/calendar.go

@@ -30,9 +30,14 @@ type (
 const (
 	// minCalendarYear is the smallest year that can appear in a calendar spec.
 	minCalendarYear = 2000
-	// maxCalendarYear is the latest year that will be recognized for calendar dates.
-	// If you're still using Temporal in 2100 please change this constant and rebuild.
+	// maxCalendarYear is the latest year that will be calculated for calendar dates.
+	// This protects against DoS from calculating far into the future. Specs can reference
+	// years beyond this limit, but actual calculation will stop here. Future server versions
+	// can safely increase this limit.
 	maxCalendarYear = 2100
+	// maxSpecYear is the largest year allowed in a schedule spec. This is set to a very
+	// large value to effectively remove the restriction while still preventing absurd values.
+	maxSpecYear = 9999
 
 	// max length of one calendar comment field
 	maxCommentLen = 200
@@ -229,7 +234,7 @@ func parseCalendarToStructured(cal *schedulepb.CalendarSpec) (*schedulepb.Struct
 		DayOfWeek:  makeRangeOrNil(cal.DayOfWeek, "DayOfWeek", "*", 0, 7, parseModeDow),
 		DayOfMonth: makeRangeOrNil(cal.DayOfMonth, "DayOfMonth", "*", 1, 31, parseModeInt),
 		Month:      makeRangeOrNil(cal.Month, "Month", "*", 1, 12, parseModeMonth),
-		Year:       makeRangeOrNil(cal.Year, "Year", "*", minCalendarYear, maxCalendarYear, parseModeYear),
+		Year:       makeRangeOrNil(cal.Year, "Year", "*", minCalendarYear, maxSpecYear, parseModeYear),
 		Comment:    cal.Comment,
 	}
 	if len(errs) > 0 {

service/worker/scheduler/spec.go

@@ -216,7 +216,7 @@ func validateStructuredCalendar(scs *schedulepb.StructuredCalendarSpec) error {
 	checkRanges(scs.Hour, "Hour", 0, 23)
 	checkRanges(scs.DayOfMonth, "DayOfMonth", 1, 31)
 	checkRanges(scs.Month, "Month", 1, 12)
-	checkRanges(scs.Year, "Year", minCalendarYear, maxCalendarYear)
+	checkRanges(scs.Year, "Year", minCalendarYear, maxSpecYear)
 	checkRanges(scs.DayOfWeek, "DayOfWeek", 0, 6)
 
 	if len(scs.Comment) > maxCommentLen {

service/worker/scheduler/spec_test.go

@@ -110,7 +110,6 @@ func (s *specSuite) TestCanonicalize() {
 		{DayOfWeek: []*schedulepb.Range{{Start: 7}}},
 		{DayOfWeek: []*schedulepb.Range{{Start: 6, End: 7}}},
 		{Year: []*schedulepb.Range{{Start: 1999}}},
-		{Year: []*schedulepb.Range{{Start: 2112}}},
 	} {
 		_, err = canonicalizeSpec(&schedulepb.ScheduleSpec{
 			StructuredCalendar: []*schedulepb.StructuredCalendarSpec{scs},
@@ -494,3 +493,16 @@ func (s *specSuite) TestSpecJitterSeed() {
 		time.Date(2022, 3, 24, 0, 39, 16, 922000000, time.UTC),
 	)
 }
+
+func (s *specSuite) TestSpecFarFutureYear() {
+	s.checkSequenceFull(
+		"",
+		&schedulepb.ScheduleSpec{
+			Calendar: []*schedulepb.CalendarSpec{
+				{Hour: "12", Minute: "0", DayOfMonth: "1", Month: "1", Year: "2150"},
+			},
+		},
+		time.Date(2099, 1, 1, 0, 0, 0, 0, time.UTC),
+		time.Time{}, // returns zero time since 2150 is beyond calculation bound
+	)
+}