this.file.name.startsWith(file.ctime.date().toString())
This is an advanced filter for a base. It returns files that have a creation date that equals the beginning of the note title of the current file*. It works also if you have text in the title, so not a pure date title (daily note).
This solves the issue that with a simpler filter (file.ctime == this.file.name) only pure dates from daily notes work.
Example: I embed my base in the note “2025-10-27 Meeting”. The base then returns all files that I have created on the 2025-10-27. This pairs well with other filters like from a specific folder/property/tag.
*This filter is for making a dynamic base: it relates to whatever is the current file. The current file can be either the file that the base is embedded in or the file that is opened while the base tab is in the sidebar. You can see the “this.file” part in my filter.
For official reference see the obsidian documentation with the header " Access properties of the current file".
It is equal to the Dataview query:
WHERE file.cday = this.file.day