Something I've been struggling with for a while. My current workaround which works decently (also a little specific to the situation) is to have a middle agent that compiles the information I need to execute a function and my middle agent has access to the current date. So if the customer says tomorrow the middle agent will make a datetime object/string for tomorrow based on today and I use that to search my calendar events. Similarly if the customer says morning/evening, next week Thursday etc...