[bugfix][ryan] update date.js to account for months with different number of days - if the date object is in a month with 31 days, this.setMonth() will screw up the month representation
[bugfix][ryan] update date.js to account for months with different number of days
- if the date object is in a month with 31 days, this.setMonth() will screw up the month representation

GovTechSG/butler-bot,GovTechSG/butler-bot