We’ve fixed an error with the observance of Yom HaShoah occurring adjacent to Shabbat. This year Yom HaShoah begins on Sunday, 7 April 2013 at sundown.
Previously Hebcal always used the date of the 27th of Nisan.
When the actual date of Yom Hashoah falls on a Friday, the state of Israel observes Yom Hashoah on the preceding Thursday. When it falls on a Sunday, Yom Hashoah is observed on the following Monday.