The sectionals that are displayed in ForeFlight are updated when the FAA publishes a new sectional, which is typically on a 6 month cycle. We provide downloads in-app for the updated charts about 5 calendar days before their valid date timeframe begins.
For each individual sectional chart, you can see the date that the updated version will be valid in the collar data. You can go SETTINGS on the Maps page (gear icon at top left), select MAP TOUCH ACTION, and BRING CHART TO FRONT WITH LEGENDS. When you tap on a sectional, the margins will display with the information that you are looking for.
Image 1. Tap the Map SETTINGS button (looks like gear) and then tap MAP TOUCH ACTION.
Image 2. From drop-down, select BRING CHART TO FRONT WITH LEGENDS.
Please see the screenshot of this Dallas - Fort Worth Sectional showing the effective date and any included amendments.
Image 3. Chart showing effective dates.