/// <summary>
/// Returns the particular date in the specified year
/// on which the daylight saving time period applies.
/// </summary>
private DateTime GetParticularDay(int year, DaylightLimit rule)
{
if (!rule.Enabled)
{
return(DateTime.MinValue);
}
// Get the first occurence of the requested weekday
DateTime result = new DateTime(year, rule.Month, 1,
rule.Hour, rule.Minute, rule.Second,
rule.Milliseconds, DateTimeKind.Local);
int diff = rule.DayOfWeek - (int)result.DayOfWeek;
if (diff < 0)
{
diff += 7;
}
result = result.AddDays(diff);
// Get the day when the daylight time change applies
result = result.AddDays((rule.Day - 1) * 7);
if (result.Month == rule.Month)
{
return(result);
}
return(result.AddDays(-7.0));
}
/// <summary>
/// Returns the particular date in the specified year
/// on which the daylight saving time period applies.
/// </summary>
private DateTime GetParticularDay(int year, DaylightLimit rule)
{
DateTime result = DateTime.MinValue;
if (rule.IsEmpty)
{
return(result);
}
// Get the first and last day of the month
DateTime first = new DateTime(year, rule.Month, 1,
rule.Hour, rule.Minute, rule.Second,
rule.Milliseconds, DateTimeKind.Local);
DateTime last = first;
try
{
last = last.AddMonths(1).AddDays(-1);
}
catch (ArgumentOutOfRangeException)
{
last = DateTime.MaxValue;
}
// Get the number of Sundays in the month
int sunday = (first.DayOfWeek == DayOfWeek.Sunday) ?
1 : 7 - (int)first.DayOfWeek + 1;
int numberOfSundays = (int)Math.Floor(
(last.Day - sunday) / 7.0) + 1;
// Get the day when the daylight time change applies
if (numberOfSundays <= 4)
{
int dif = rule.DayOfWeek - ((int)first.DayOfWeek);
if (dif < 0)
{
dif += 7;
}
dif += 7 * (numberOfSundays - 1);
if (dif > 0)
{
return(first.AddDays(dif));
}
return(first);
}
else
{
int dif = ((int)last.DayOfWeek) - rule.DayOfWeek;
if (dif < 0)
{
dif += 7;
}
if (dif > 0)
{
return(last.AddDays(-dif));
}
return(last);
}
}