Use a "count of" summary field to count your records.
Sort them by the date field.
In your chart, chart the summary field and specify these charting options:
Use data from current found set
Show data points from groups of records when sorted.
How do I use a "count of" summary field to count records?
Add a field of type summary to your table. Specify the "count of" option. Select any field in the table that is never empty. (Often, this makes the primary key field the obvious choice since it would never be empty.)