The day Monica was to testify was when he decided (and may have actually done) to bomb Serbia. I just checked.
IMPEACHMENT OF BILL CLINTON - Clinton was impeached on December 19, 1998, by the House of Representatives on grounds of perjury to a grand jury (by a 228–206 vote)[17] and obstruction of justice (by a 221–212 vote).
OPERATION DESERT FOX - The December 1998 bombing of Iraq (code-named Operation Desert Fox) was a major four-day bombing campaign on Iraqi targets from December 16, 1998, to December 19, 1998, by the United States and United Kingdom.