//http://facebooktoolkit.codeplex.com/
//http://facebooktoolkit.codeplex.com/license
using System;
namespace Facebook.Utility
{
///<summary>
/// Contains helper for converting to and from the date formats provided by facebook
///</summary>
public static class DateHelper
{
///<summary>
/// Returns a datetime corresponding to 1/1/1970
///</summary>
public static DateTime BaseUTCDateTime
{
get { return new DateTime(1970, 1, 1, 0, 0, 0); }
}
///<summary>
/// Event dates are stored by assuming the time which the user input was in Pacific
/// time (PST or PDT, depending on the date), converting that to UTC, and then
/// converting that to Unix epoch time. This algorithm reverses that process.
///</summary>
public static DateTime ConvertUnixTimeToDateTime(long secondsSinceEpoch)
{
DateTime utcDateTime = BaseUTCDateTime.AddSeconds(secondsSinceEpoch);
int pacificZoneOffset = utcDateTime.IsDaylightSavingTime() ? -7 : -8;
return utcDateTime.AddHours(pacificZoneOffset);
}
/// <summary>
/// Convert datetime to UTC time, as understood by Facebook.
/// </summary>
/// <param name="dateToConvert">The date that we need to pass to the api.</param>
/// <returns>The number of seconds since Jan 1, 1970.</returns>
public static long ConvertDateToFacebookDate(DateTime dateToConvert)
{
return (long)((dateToConvert - BaseUTCDateTime).TotalSeconds);
}
/// <summary>
/// Convert UTC time, as returned by Facebook, to localtime.
/// </summary>
/// <param name="secondsSinceEpoch">The number of seconds since Jan 1, 1970.</param>
/// <returns>Local time.</returns>
internal static DateTime ConvertDoubleToDate(double secondsSinceEpoch)
{
#if !SILVERLIGHT
return TimeZone.CurrentTimeZone.ToLocalTime(BaseUTCDateTime.AddSeconds(secondsSinceEpoch));
#else
return TimeZoneInfo.ConvertTime(BaseUTCDateTime.AddSeconds(secondsSinceEpoch), TimeZoneInfo.Local);
#endif
}
//Event dates are stored by assuming the time which the user input was in Pacific
// time (PST or PDT, depending on the date), converting that to UTC, and then
// converting that to Unix epoch time. This algorithm reverses that process.
internal static DateTime ConvertDoubleToEventDate(double secondsSinceEpoch)
{
DateTime utcDateTime = BaseUTCDateTime.AddSeconds(secondsSinceEpoch);
int pacificZoneOffset = utcDateTime.IsDaylightSavingTime() ? -7 : -8;
return utcDateTime.AddHours(pacificZoneOffset);
}
/// <summary>
/// Convert datetime to UTC time, as understood by Facebook.
/// </summary>
/// <param name="dateToConvert">The date that we need to pass to the api.</param>
/// <returns>The number of seconds since Jan 1, 1970.</returns>
internal static double? ConvertDateToDouble(DateTime? dateToConvert)
{
return dateToConvert != null ? new double?((dateToConvert.Value - BaseUTCDateTime).TotalSeconds) : null;
}
}
}
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