Function std.datetime.systime.SysTime.toISOString
Converts this SysTime to a string with the format
        YYYYMMDDTHHMMSS.FFFFFFFTZ (where F is fractional seconds and TZ is time
        zone).
						
				string toISOString() nothrow @safe const;
				
				
				void toISOString(W)
				(
				
				  ref W writer
				
				) const
				
				if (isOutputRange!(W, char));
						
					
				Note that the number of digits in the fractional seconds varies with the number of fractional seconds. It's a maximum of 7 (which would be hnsecs), but only has as many as are necessary to hold the correct value (so no trailing zeroes), and if there are no fractional seconds, then there is no decimal point.
        If this SysTime's time zone is
        LocalTime, then TZ is empty. If its time
        zone is UTC, then it is "Z". Otherwise, it is the offset from UTC
        (e.g. +0100 or -0700). Note that the offset from UTC is not enough
        to uniquely identify the time zone.
Time zone offsets will be in the form +HHMM or -HHMM.
        Warning:
            Previously, toISOString did the same as toISOExtString and
            generated +HH:MM or -HH:MM for the time zone when it was not
            LocalTime or
            UTC, which is not in conformance with
            ISO 8601 for the non-extended string format. This has now been
            fixed. However, for now, fromISOString will continue to accept the
            extended format for the time zone so that any code which has been
            writing out the result of toISOString to read in later will continue
            to work. The current behavior will be kept until July 2019 at which
            point, fromISOString will be fixed to be standards compliant.
Parameters
| Name | Description | 
|---|---|
| writer | A characcepting
            output range | 
Returns
A string when not using an output range; void otherwise.
Example
import core