This question resolves to the day on which the 

unequivocally reports that a full-scale invasion of Rafah by Israel has begun.

Reports of air strikes, raids, covert operations, incursions, etc will not be sufficient for a resolution. In general, ambiguous situations in which the NYT does not specifically describe events as a "full-scale invasion" will not be sufficient to resolve this market. 

This market will resolve to the day on which the qualifying reporting is published, which may not be the same day that the reported events occurred. 

If a ground invasion begins on Friday night but the Times does not report on it until Saturday morning, this market resolves to Saturday. Op-Eds and similar will not be sufficient for resolution.

Resolution will be based on Eastern Time (UTC -04:00). If there is no invasion reported before May 20th, this market resolves to "Not before Monday, May 20th".