Function diff

static/plugins/chart.js/Chart.bundle.js:17973–18005

(input, units, asFloat)

    }

    function diff (input, units, asFloat) {
        var that,
            zoneDelta,
            output;

        if (!this.isValid()) {
            return NaN;
        }

        that = cloneWithOffset(input, this);

        if (!that.isValid()) {
            return NaN;
        }

        zoneDelta = (that.utcOffset() - this.utcOffset()) * 6e4;

        units = normalizeUnits(units);

        switch (units) {
            case 'year': output = monthDiff(this, that) / 12; break;
            case 'month': output = monthDiff(this, that); break;
            case 'quarter': output = monthDiff(this, that) / 3; break;
            case 'second': output = (this - that) / 1e3; break; // 1000
            case 'minute': output = (this - that) / 6e4; break; // 1000 * 60
            case 'hour': output = (this - that) / 36e5; break; // 1000 * 60 * 60
            case 'day': output = (this - that - zoneDelta) / 864e5; break; // 1000 * 60 * 60 * 24, negate dst
            case 'week': output = (this - that - zoneDelta) / 6048e5; break; // 1000 * 60 * 60 * 24 * 7, negate dst
            default: output = this - that;
        }

        return asFloat ? output : absFloor(output);
    }

    function monthDiff (a, b) {
        // difference in months