How to do Remainder in C# Windows Application

Question

i have an application that would be have remainder or you can say as to-do-list
i want to add for example meetings in specific  date and time as i want , and i want my application to remainder me before that date and time as i do it ,maybe MessageBox appear to tell me that i have meeting for example !! or in any other way to notify me

how can i do that in c# !!