Parse failure on dates before 1970 with an inline timezone

[ruskiyos]

invalid_date.txt

• PHP Version: 7.1.8
• PHP date.timezone: America/Los_Angeles
• ICS Parser Version: dev-master
• Linux

Description of the Issue:

When parsing an event with a inline timezone, earlier than 1970, the parser fails.
DTSTART;TZID=America/Los_Angeles:00011212T020000

Steps to Reproduce:

Parse attached file.
Error returned: The timezone could not be found in the database

Notes

File: ICal.php
Line: 661

if less than year, parse raw string, even though it should continue on to next if statement

// A Unix timestamp cannot represent a date prior to 1 Jan 1970
$year = $date[2];
if ($year <= self::UNIX_MIN_YEAR) {
    $dateTime = new \DateTime($icalDate, new \DateTimeZone($this->defaultTimeZone));
} else {
    if ($forceTimeZone) {
...