BUG: Fix timedelta64+Timestamp, closes #24775
- [x] closes #24775
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=h1) Report
> Merging [#26916](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/baa77c33fb71c29acea21ba06adaf426ed4cb561?src=pr&el=desc) will **decrease** coverage by `50.76%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26916/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=tree)

```diff
@@             Coverage Diff             @@
##           master   #26916       +/-   ##
===========================================
- Coverage   91.87%    41.1%   -50.77%     
===========================================
  Files         180      180               
  Lines       50712    50712               
===========================================
- Hits        46590    20845    -25745     
- Misses       4122    29867    +25745
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `?` | |
| #single | `41.1% <ø> (-0.08%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/formats/latex.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvbGF0ZXgucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/plotting/\_matplotlib/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19tYXRwbG90bGliL19faW5pdF9fLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/gcs.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2djcy5weQ==) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/sas/sas\_constants.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfY29uc3RhbnRzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/core/groupby/categorical.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ3JvdXBieS9jYXRlZ29yaWNhbC5weQ==) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/tseries/plotting.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvcGxvdHRpbmcucHk=) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/s3.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3MzLnB5) | `0% <0%> (-100%)` | :arrow_down: |
| [pandas/io/formats/html.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2Zvcm1hdHMvaHRtbC5weQ==) | `0% <0%> (-99.37%)` | :arrow_down: |
| [pandas/io/sas/sas7bdat.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXM3YmRhdC5weQ==) | `0% <0%> (-91.16%)` | :arrow_down: |
| [pandas/io/sas/sas\_xport.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL3Nhcy9zYXNfeHBvcnQucHk=) | `0% <0%> (-90.1%)` | :arrow_down: |
| ... and [132 more](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=footer). Last update [baa77c3...9666416](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=h1) Report
> Merging [#26916](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/83fe8d78b6b086f3ceabe81cd420a3c7affe9aba?src=pr&el=desc) will **decrease** coverage by `<.01%`.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/26916/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #26916      +/-   ##
==========================================
- Coverage   91.99%   91.98%   -0.01%     
==========================================
  Files         180      180              
  Lines       50774    50774              
==========================================
- Hits        46712    46707       -5     
- Misses       4062     4067       +5
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.63% <ø> (ø)` | :arrow_up: |
| #single | `41.83% <ø> (-0.08%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `88.88% <0%> (-11.12%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `96.89% <0%> (-0.12%)` | :arrow_down: |
| [pandas/util/testing.py](https://codecov.io/gh/pandas-dev/pandas/pull/26916/diff?src=pr&el=tree#diff-cGFuZGFzL3V0aWwvdGVzdGluZy5weQ==) | `90.84% <0%> (-0.11%)` | :arrow_down: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=footer). Last update [83fe8d7...534db4c](https://codecov.io/gh/pandas-dev/pandas/pull/26916?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Fixed typo, determined there's only a couple other dedicated Timestamp arith tests, moved them over to the appropriate place and parametrized them.

We've done a good job at making tslibs self-contained, less so with the tests.  At some point I'd like to change that, hopefully make it easier to identify gaps in isolated coverage. > Fixed typo, determined there's only a couple other dedicated Timestamp arith tests, moved them over to the appropriate place and parametrized them.
> 
> We've done a good job at making tslibs self-contained, less so with the tests. At some point I'd like to change that, hopefully make it easier to identify gaps in isolated coverage.

yep i here ya increasing coverage always +1 i have some open requests here > i have some open requests here

I think your open request is that we put this with the Timedelta arithmetic tests.  But doing so would break the organization of the Timedelta tests.   no my requests are to parametrize over a Timedelta the tests u added > no my requests are to parametrize over a Timedelta the tests u added

added. thanks @jbrockmendel 