This MAR10 Day, Nintendo Switch Online members can enjoy a 14-day free trial of the service. During this time, they can play classic games featuring Mario on their console or listen to nostalgic soundtracks on their mobile device using the Nintendo Music app.
Additionally, players who join the My Nintendo Mario Kart 8 Deluxe Community Challenge have the chance to receive 310 Platinum Points if the goal of one million combined laps is reached by all global players. To participate, simply enter code 1152-2501-4827 in-game and check out my.nintendo.com for more details.
New to Switch Online? Head over to My Nintendo to claim your free trial membership and get in on the fun before March 17 at 11:00 p.m. PT. Note that this limited-time offer requires a Nintendo Account, has some restrictions, and may automatically convert to an auto-renewing membership at the end of the trial.
Source: https://www.nintendo.com/us/whatsnew/play-together-and-have-fun-online-this-mar10-day-with-a-14-day-free-trial-membership-of-nintendo-switch-online