Fix warning Day.delta is deprecated

[rubencalje]

This PR fixes the following warning you get in Pandas version 2.2.1 when loading a model from file or pastastore:
FutureWarning: Day.delta is deprecated and will be removed in a future version. Use pd.Timedelta(obj) instead

Short Description

Add a short description describing the pull request (PR) here.

Checklist before PR can be merged:

• closes issue #xxxx
• is documented
• Format code with Black formatting
• type hints for functions and methods
• tests added / passed
• Example Notebook (for new features)
• Remove output for all notebooks with changes

[codacy-production]

Coverage summary from Codacy

See diff coverage on Codacy

Coverage variation	Diff coverage
✅ +0.45% (target: +0.00%)	✅ 100.00%

Coverage variation details

	Coverable lines	Covered lines	Coverage
Common ancestor commit (67392f3)	6087	4582	75.28%
Head commit (2288d99)	6126 (+39)	4639 (+57)	75.73% (+0.45%)

Coverage variation is the difference between the coverage for the head and common ancestor commits of the pull request branch: <coverage of head commit> - <coverage of common ancestor commit>

Diff coverage details

	Coverable lines	Covered lines	Diff coverage
Pull request (#713)	20	20	100.00%

Diff coverage is the percentage of lines that are covered by tests out of the coverable lines that the pull request added or modified: <covered lines added or modified>/<coverable lines added or modified> * 100%

See your quality gate settings    Change summary preferences

_{You may notice some variations in coverage metrics with the latest Coverage engine update. For more details, visit the documentation}