"National Day for Truth and Reconciliation" means september 30th; a statutory holiday in canada, for the recognition of the cultural genocide of indigenous peoples in canada enacted by the colonizers, especially that caused by the residential school system; declared as a law in 2020, and first observed in 2021. It is one of many casual words teens pick up from friends, social media, music or sport, and on its own it carries no particular warning. If you hear your teen use it, it is fair to ask what they mean by it in their friend group, since meanings drift quickly. Asking out of curiosity rather than alarm tends to keep the conversation open and useful.