long ToUnixTimestamp(System.DateTime dt){
    DateTime unixRef = new DateTime(1970, 1, 1, 0, 0, 0);
    return (dt.Ticks - unixRef.Ticks) / 10000000;
}
 
DateTime FromUnixTimestamp(long timestamp){
    DateTime unixRef = new DateTime(1970, 1, 1, 0, 0, 0);
    return unixRef.AddSeconds(timestamp);
}