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Flask - Convert date from yyyy-mm-dd to dd-mm-yyyy in jinja2


We can change the date format using Jinja2 filters. Jinja2 filters are used to transform data into another.

Configure Jinja2 environment in the following manner. 
#define function for convert yyyy-mm-dd to dd-mm-yyyy
def format_datetime(value, format="%d-%m-%Y"):
    if value is None:
        return ""
    return datetime.strptime(value,"%Y-%m-%d").strftime(format)

#configured Jinja2 environment with user defined
app.jinja_env.filters['date_format']=format_datetime

Use the filter variable in the following manner. 
<p>{{ row['cdate'] | date_format }}</p>
<p>{{ row['cdate'] | date_format("%b %d - %Y") }}</p>

The complete code is as follows

app.py 
from flask import Flask,render_template
from datetime import datetime

app=Flask(__name__)

#define function for convert yyyy-mm-dd to dd-mm-yyyy
def format_datetime(value, format="%d-%m-%Y"):
    if value is None:
        return ""
    return datetime.strptime(value,"%Y-%m-%d").strftime(format)

#configured Jinja2 environment with user defined
app.jinja_env.filters['date_format']=format_datetime

@app.route("/")
@app.route("/index")
def index():
    data={'cdate':'2022-01-17'}
    return render_template("index.html",row=data)
    
if(__name__=='__main__'):
    app.run(debug=True)
index.html 
<!-- Output Format :  17-01-2022 -->
<p>{{ row['cdate'] | date_format }}</p>

<!-- Output Format :  17 Jan 2022 -->
<p>{{ row['cdate'] | date_format("%b %d - %Y") }}</p>

<!-- Output Format :  Mon January 2022 -->
<p>{{ row['cdate'] | date_format("%a - %B - %Y") }}</p>