Added a helper method for date normalisation

[shubham-thanki-at-sandbox]

This pull request refactors the DateUtil class to improve code maintainability and consistency when handling date inputs. The main change is the introduction of a new normalizeDate helper method, which centralizes the logic for converting numeric timestamps to Date objects. This method is now used throughout the class, replacing repeated inline checks.

Refactoring for date normalization:

• Added a protected static normalizeDate method to DateUtil, which converts a number to a Date object or returns the Date as is. This centralizes and simplifies date normalization logic.
• Updated all methods in DateUtil that previously checked and converted numeric date arguments inline to use the new normalizeDate method instead, improving readability and reducing code duplication. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10]

Version bump:

• Incremented the package version from 2.0.5 to 2.0.6 in package.json to reflect these internal improvements.