I'm trying to split a df by datetime. The df is indexed on the datetime variable. Essentially, I can do:

```
first = df['2020-04-09':'2020-04-21']
second  = df['2020-04-22':'2020-05-08']

```

and that yields my desired result of 2 dfs, each with their respective datetime range's worth of data.

However, I'd like a way to allow for easier editing at the top of the script by assigning the datetime ranges to local variables. Ideally something like this:

```
first_dates = '2020-04-09':'2020-04-21'
second_dates = '2020-04-22':'2020-05-08'

```

Such that later on I'm able to use something like:

```
first = df[first_dates]
second = df[second_dates]

```

and yield the same result of 2 dfs with their respective date ranges worth of data.