pandas split year from a year-date-time column

I have a dataframe ‘df’ with one column called ‘date_time’ that has values in this format "2018-01-01T00:00:00-05:00".
I want to split it so I have just the year "2018" in a new column.

I tried
df[‘year’] = df["date_time"].str.split("-", n=1, expand = False)
I get a new column called ‘year’ with a list [2018, 01-01T00:00:00-05:00]
But I want to split it so I have just the year 2018 in the new column.

>Solution :

IIUC use:

df['year'] = pd.to_datetime(df['date_time'], error="coerce").dt.year