dates.js

function getSopMonth (asText = false) {
    let date = new Date();
    let month = date.getUTCMonth() + 1; // date.getMonth() is zero indexed.

    let names = ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'];

    if (asText) {
        return names[month];
    }
    
    return month + 1; // zero index so we get the correct month integer.
}

function getSopQuarter () {
	return getQuarter((new Date()).getUTCMonth() + 1);
}

function getQuarter (month) {
	let quarters = [[1,2,3], [4,5,6], [7,8,9], [10,11,12]];
	let words = ['First', 'Second', 'Third', 'Fourth'];
    let q = Math.ceil(month / 3);
    return {
    	name: words[q - 1],
    	range: quarters[q - 1],
    	number: q
    }
}

function isOpen (sop) {
	if (!sop.last_submitted) return true;
	
	// Get current date
	let current = new Date();
	
	// Get first day of the month
	let first_day = new Date(current.getFullYear(), current.getUTCMonth(), 1);
	
	// Get last submitted date
	let last_date = new Date(`${sop.last_submitted.split('T')[0]}T00:00:00`); // Reset time on date to prevent time mismatch issues.
	
	if (sop.frequency === 'quarterly') {
		// Get actual month integer
		let current_month = current.getUTCMonth() + 1;
		
		// Get quarter based on month
		let quarter = this.getQuarter(current_month);
		
		return quarter.range.indexOf(last_date.getUTCMonth()) === -1 // last submitted month is not in current quarter
			&& quarter.range.indexOf(current_month) > 0 // current month index in quarter is greater than 0 (second or third)
			&& last_date < first_day; // last submitted date is before the first day of the current month
	}
	
	return last_date < first_day; // monthly sub last submitted date is before the first day of the current month
}

console.log(getSopQuarter());
    
console.log('Quarterly (2017-03-15) is open? %s', isOpen({
	last_submitted: '2017-03-15',
	frequency: 'quarterly'
}));

console.log('Monthly (2017-03-15) is open? %s' , isOpen({
	last_submitted: '2017-03-15',
	frequency: 'monthly'
}));

console.log('Monthly (2017-04-01) is open? %s' , isOpen({
	last_submitted: '2017-04-01',
	frequency: 'monthly'
}));

console.log('Monthly (2017-04-15) is open? %s' , isOpen({
	last_submitted: '2017-04-15',
	frequency: 'monthly'
}));

console.log('Null date is open? %s' , isOpen({
	last_submitted: null,
	frequency: 'monthly'
}));

console.log('Empty string date is open? %s' , isOpen({
	last_submitted: '',
	frequency: 'monthly'
}));