The TODAY() function in Excel returns the current day. The DATEVALUE() function converts a date string into a serial value. While helpful for many features within Excel, Adobe strongly recommends against using these functions as part of Report Builder scheduled requests. Adobe Customer Care does not support troubleshooting requests using either of these functions.
Scheduled reports are processed on servers that likely do not share time zones as the report suite. The TODAY() a user expects and the TODAY() the processing server uses can often be different. Also, the date used is based on when processing starts. If many reports are run simultaneously, the date can change between the time it is requested and when it starts processing due to delays. This issue is present if the scheduled time is close to midnight.
Scheduled reports are also processed on servers that likely do not share date syntax. For example, "7/1/2016" can refer to July 1 or January 7 depending on your country or region. Using the DATEVALUE() function on this date would result in differing serial values depending on the computer that executes it.
As an alternative to using these Excel functions, Adobe highly recommends using date ranges within Report Builder requests. On the first page of the request wizard, select 'Preset Dates' in the dropdown, then under Commonly Used Dates, select 'Today' or another desired date range. This setting takes the time of the report suite at the time it was run, and not the time of the server processing the information.