2.1.39 [ECMA-262/9:2018] Section Date Time String Format

V0125: A date-time without a time zone offset is interpreted incorrectly

The specification states:

 ... Date Time String Format
     ECMAScript defines a string interchange format for date-times based upon a 
     simplification of the ISO 8601 Extended Format. The format is as follows: 
     Where the fields are as follows:
         YYYY is the decimal digits of the year 0000 to 9999 in the [proleptic] Gregorian 
         Z is the time zone offset specified as "Z" (for UTC) or either "+" or "-" 
         followed by a time expression HH:mm

EdgeHTML Mode

When the date-time string does not include a time zone offset, the time is taken, incorrectly, to be UTC, not local time. For example, if the date-time string is "2015-10-01", it is taken to mean:

    Wed Sep 30 2015 17:00:00 GMT-0700 (Pacific Daylight Time)

According to the specification, it should be taken as:

    Thu Oct 01 2015 00:00:00 GMT-0700 (Pacific Daylight Time)