Entry::find()->startDate('>='. $someTime).endTime('<='.$someOtherTime).all();

Entry::find()
    ->variantOne('<=' .  Db::prepareDateForDb(new DateTime())) <-- DateTime object
    ->variantTwo('<=' . time())  <-- as timestamp
    ->variantThree('<=' . (new DateTime())->format('U')) <-- timestamp as well
    ->variant(['and', '<=' . time() , '>=' . time() - 3600]) <-- entries within the last hour