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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
namespace System
{
partial class TimeZoneInfo
{
//
// TransitionTimeToDateTime -
//
// Helper function that converts a year and TransitionTime into a DateTime
//
static internal DateTime TransitionTimeToDateTime(Int32 year, TransitionTime transitionTime) {
DateTime value;
DateTime timeOfDay = transitionTime.TimeOfDay;
if (transitionTime.IsFixedDateRule) {
// create a DateTime from the passed in year and the properties on the transitionTime
// if the day is out of range for the month then use the last day of the month
Int32 day = DateTime.DaysInMonth(year, transitionTime.Month);
value = new DateTime(year, transitionTime.Month, (day < transitionTime.Day) ? day : transitionTime.Day,
timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
}
else {
if (transitionTime.Week <= 4) {
//
// Get the (transitionTime.Week)th Sunday.
//
value = new DateTime(year, transitionTime.Month, 1,
timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
int dayOfWeek = (int)value.DayOfWeek;
int delta = (int)transitionTime.DayOfWeek - dayOfWeek;
if (delta < 0) {
delta += 7;
}
delta += 7 * (transitionTime.Week - 1);
if (delta > 0) {
value = value.AddDays(delta);
}
}
else {
//
// If TransitionWeek is greater than 4, we will get the last week.
//
Int32 daysInMonth = DateTime.DaysInMonth(year, transitionTime.Month);
value = new DateTime(year, transitionTime.Month, daysInMonth,
timeOfDay.Hour, timeOfDay.Minute, timeOfDay.Second, timeOfDay.Millisecond);
// This is the day of week for the last day of the month.
int dayOfWeek = (int)value.DayOfWeek;
int delta = dayOfWeek - (int)transitionTime.DayOfWeek;
if (delta < 0) {
delta += 7;
}
if (delta > 0) {
value = value.AddDays(-delta);
}
}
}
return value;
}
} // TimezoneInfo
} // namespace System
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