If you have iCloud turned on in the DayMap preferences, your data is at: /Users//Library/MobileDocuments/2WFZT4HWJN~com~whetstoneapps~daymap/DayMap.b_storedata
If you are not using iCloud, your data is at: /Users//Library/Containers/com.whetstoneapps.daymap/data/Library/Application Support/DayMap/DayMap.b_storedata
Hint: A quick way to get into your library. While in Finder, hold down the option key and click on Go in the Apple menu. Click on library.