MFCで日数の差分計算

COleDateTime nowdatetime = COleDateTime::GetCurrentTime();
COleDateTime predatetime(2020,4, 14,0,0,0);
COleDateTimeSpan span(nowdatetime - predatetime);

// 3日以内チェック 
if (span.GetTotalDays() <= 3) {
	...
}