BUG: resolving issue 16357 - added a check to see if input is pandas.NaT
 - [x] closes #16357 
 - [ ] tests added / passed
 - [x] passes ``git diff upstream/master --name-only -- '*.py' | flake8 --diff``
 - [ ] whatsnew entry

# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=h1) Report
> Merging [#16501](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/e81f3cc30725443a1d36ec27279f3fec4eed60ec?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16501/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16501      +/-   ##
==========================================
+ Coverage   90.43%   90.43%   +<.01%     
==========================================
  Files         161      161              
  Lines       51045    51046       +1     
==========================================
+ Hits        46161    46162       +1     
  Misses       4884     4884
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.27% <100%> (ø)` | :arrow_up: |
| #single | `40.16% <0%> (-0.01%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.33% <100%> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16501?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/16501?src=pr&el=footer). Last update [e81f3cc...7fb8395](https://codecov.io/gh/pandas-dev/pandas/pull/16501?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/16501?src=pr&el=h1) Report
> Merging [#16501](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/7d9d6d3465d1c102c69d799161ebd9e28540acba?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/16501/graphs/tree.svg?src=pr&token=eZ4WkYLtcO&width=650&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #16501      +/-   ##
==========================================
+ Coverage      91%      91%   +<.01%     
==========================================
  Files         161      161              
  Lines       49308    49309       +1     
==========================================
+ Hits        44871    44875       +4     
+ Misses       4437     4434       -3
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `88.78% <100%> (+0.02%)` | :arrow_up: |
| #single | `40.19% <0%> (-0.07%)` | :arrow_down: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.33% <100%> (ø)` | :arrow_up: |
| [pandas/io/gbq.py](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree#diff-cGFuZGFzL2lvL2dicS5weQ==) | `25% <0%> (-58.34%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.75% <0%> (-0.1%)` | :arrow_down: |
| [pandas/plotting/\_converter.py](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=tree#diff-cGFuZGFzL3Bsb3R0aW5nL19jb252ZXJ0ZXIucHk=) | `65.05% <0%> (+1.81%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/16501?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/16501?src=pr&el=footer). Last update [7d9d6d3...16a1e43](https://codecov.io/gh/pandas-dev/pandas/pull/16501?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 can you rebase and update?

couple of comments. can you u rebase and update & change release note to 0.21.0 can you rebase / update according to comments can you add the test from the issue & rebase closing as stale. if you want to finish up. pls ping and we can reopen.