C＃DateTime.ToString（）方法是否存在时区问题？

Question

My server is in UTC time zone, and my local system is in another time zone. I have a datetime object, pointing to the first second of a particular date, say the 7th of Jan, 2018 ie 07-01-2019 00:00:00 . If I call the toString("dd MMM yyyy") method on this object and return it to my local system and display it, I observe that the date is off by a day, showing 6 Jan 2019. Could you explain why it might be so?

EDIT:Initially, my intention in asking the question was to know if the dateTime.ToString() method had any noticeable problems. Could someone please explain to me why this behaves the way it does?

My testing of the problem revealed that the error is reproducible only when the serve hosting the webpage & the client interacting with the webpage are in different time zones. My client is in IST & the server is in UTC. Suppose I pick 29th Jan, 2019 & 7th Feb, 2019 as the start & end dates respectively.

The client side sends the following as parameters to the API. I have noticed by switching to different timezones that the parameters sent are in UTC only.

fromDate: "2019-01-28T18:30:00.000Z"
toDate: "2019-02-06T18:30:00.000Z"

The API accepts them and does the following

{
    DateTime utcStart = DateTime.SpecifyKind(Convert.ToDateTime(fromDate), 
    DateTimeKind.Unspecified);
    DateTime utcEnd = DateTime.SpecifyKind(Convert.ToDateTime(toDate), 
    DateTimeKind.Unspecified);
    dummyMethod(utcStart,utcEnd,true, null, out strDuration);
}

dummyMethod(DateTime? fromDate, DateTime? toDate, Boolean convertToUTC, int? timeZoneKey, out string displayString)
{
    DateTime centerStartDate = GetCurrentTime(timeZoneKey).Date;
    DateTime centerEndDate = GetCurrentTime(timeZoneKey).Date;

    if (fromDate.HasValue)
        centerStartDate = fromDate.Value.Date;
    if (toDate.HasValue)
        centerEndDate = toDate.Value.Date;

    displayString = centerStartDate.ToString("dd MMM yyyy") + " - " + centerEndDate.ToString("dd MMM yyyy");
}

The displayString is directly returned via JSON, and the displayString is where things seem to be going wrong.

TIA

Answer 1

如果要获取服务器/ Utc时间的日期，则必须致电：

DateTime.UtcNow

Answer 2

This is because the DateTime actually stores ticks from 00:00:00 01-01-0001 AD From MSDN:

A particular date is the number of ticks since 12:00 midnight, January 1, 0001 AD (CE) in the GregorianCalendar calendar.

Because of that, the DateTime object will have the UtcTime in terms of ticks, and when you receive it in your local system, you will get the adjusted DateTime when you print DateTime.ToString();

This can be corrected by using UtcTime.

DateTime.UtcNow;