date value to serialize
a corresponding ISO8601 string representating the localtime without offset
const originalDatetimeString: string = '2021-03-25T01:00:00-07:00';
const datetimeNoOffset: Date = new Date(originalDatetimeString);
// datetimeNoOffset -> Thu Mar 25 2021 01:00:00 GMT-0700 (Pacific Daylight Time)
const serializedDatetime: string | undefined = serializeDateValue(datetimeNoOffset);
// serializedDatetime -> 2021-03-25T01:00:00
Given a date object, returns a corresponding ISO8601 representating the localtime without offset