code: public static Long toTimestampTz(String dateStr, String format, String tzStr) {
  		TimeZone tz = TIMEZONE_CACHE.get(tzStr);
  		return toTimestamp(dateStr, format, tz);
  	}
docs: Parse date time string to timestamp based on the given time zone string and format.
  Returns null if parsing failed.
  
  @param dateStr the date time string
  @param format the date time string format
  @param tzStr the time zone id string