src/m/moment.js
function normalizeUnit(unit) {
    unit = toStr(unit);

    if (unitShorthandMap[unit]) return unitShorthandMap[unit];

    return unit.toLowerCase().replace(regEndS, '');
}
function normalizeUnit(unit) {
    unit = toStr(unit);

    if (unitShorthandMap[unit]) return unitShorthandMap[unit];

    return unit.toLowerCase().replace(regEndS, '');
}
function normalizeUnit ( unit ) { unit = toStr ( unit ) ; if ( unitShorthandMap [ unit ] ) return unitShorthandMap [ unit ] ; return unit . toLowerCase ( ) . replace ( regEndS , '' ) ; }
Turn 'y' or 'years' into 'year'
Turn y or years into year