Unix Time displaying for dates between 0-9 when rendering of split headers when using a data in the Split By field

[ramirezg-web]

Bug Report

Perspective createData() interprets data correctly when dates are larger than 9. When rendering of split headers Dates between 0-9 inclusively do not render as expected when using a data in the Split By field

Steps to Reproduce:

1. find replication of issue here: https://codesandbox.io/p/sandbox/suspicious-kapitsa-8fp4lp?file=%2Findex.html%3A97%2C39
   Use Perspective Viewer to render the table
2. Manually change the parameter in createData() function to a number lower than 9 and greater than or equal to 0
3. the table renders in Unix time

Expected Result:

Expected to see table render in expected format.

Actual Result:

When the createData function has a parameter passed that is below the number 9, the rendered output appears as UNIX time.
Reproduction, https://codesandbox.io/p/sandbox/suspicious-kapitsa-8fp4lp?file=%2Findex.html%3A97%2C39

Environment:

Perspective 2.7.1
MacOS Ventura 13.6.1
Chrome Browser 120.0.6099.234 (Official Build) (x86_64)