Show complete date range in chart

I created a table of three columns -- date, person 1, and person 2. Under each person and across from each date is a value (the person's weight). The dates run from March 2 to June 9. When I turned the data in this table into a simple line chart, the chart shows data values only from May 8 to June 6. I have recreated the chart several times, thinking that I must have missed highlighting some of the cells, but I get the same results every time. What am I missing? Thanks for any help you can offer. Dick