Take a look at what happens when you insert a note with the &todays_date parameter in a drawing vs what happens if inserted in a format. In a drawing when you type in &todays_date the date appears. If you edit the properties of the note what do you see? You see the date in text format (the parameter is applied only once) you don't see the &todays_date parameter which is why the date doesn't update. If the parameter were still there the date would update as you opened the drawing on different days. In a format if &todays_date is typed in it is converted to plain text, it's not the parameter name you are seeing when you edit the properties of the note. If you place the parameter in a table on the format the table appears to keep the parameter until the format is applied to a drawing sheet. A table also appears to be handled differently than other elements if placed in a format. The date displays when the format is inserted into a drawing but notice what you get when you edit the cell properties, plain text, the parameter is applied only once. My quess as to why it doesn't show the date is that it is a drawing parameter and is not recognized by a format so it is converted to plain text (you see something similar when typing in a parameter name that is not defined, it is just converted to plain text) and it works differently than other parameters in that it is applied only once (when typed in, when inserted with a format within a table, inserting a table in a drawing).
If you want &todays_date to work outside of a table, such as within a note, you need to place it in a drawing template. A drawing format and a drawing template are two different things. The format should contain things that are part of the sheet format, such as the border and sheet markings. The drawing template contains information on view placement, dimension creation, etc.. Although you can place tables in a format it may be more appropriate to include those items in a template.
