Temporary redirect for promotion

My website will be promoting a special product for Mother's day (13 May). A landing page has been created, now I need a temporary redirect so when a user goes to the Home page, they see the promotional landing page first. On the landing page, there is a link to the home page of the site (if the user does not want to take the promotional product), this should take them to the regular home page. Previously, a developer created a redirect for this website for Valentine's Day. The code included an end date so that at the end of the promo day, the redirect stopped on its own. I just need someone to update the code to redirect users to the landing page until the end of 13th May (Australian time).