DRF3_UnixEpochDateTimeField_serializer.py

#Django 10.1 on Python 3.5

#main credit to http://stackoverflow.com/users/2089197/kevin-stone
#sub credit to http://stackoverflow.com/users/3694224/kerryz
#Questions or problems please reach me at hammadzz on github
#The serializers are timezone aware, they will check the timezone of the datetimefield object and serialize to a unix epoch timestamp (it is always in UTC). The magic piece that makes it work correctly is calendar.timegm()

#Add these serializers in serializers.py, the best practice is to make a new Django app called utils, and create a serializers.py file there which contains the code in this snippet. I have included an example using it below: 
#utils/your-django-project/utils/serializers.py
from rest_framework import serializers
from django.core.exceptions import ValidationError
import datetime
import calendar
from pytz import utc # pip install pytz

class UnixEpochDateTimeField(serializers.DateTimeField):
    
    def to_representation(self, value):
        """
        to_representation method is responsible for turning the 
        Python object into a simple, serializable value.
        Here: return epoch time for a datetime object or `None`
        """
        return self.datetime_to_epoch(value)

    def to_internal_value(self, value):
        return self.epoch_to_datetime(value)

    @staticmethod
    def datetime_to_epoch(value):
        try:
            return int(calendar.timegm(value.utctimetuple()))
        except (AttributeError, TypeError):
            return None

    @staticmethod
    def epoch_to_datetime(value):
        try:
            return datetime.datetime.utcfromtimestamp(int(value)).replace(tzinfo=utc)
        except (ValueError, TypeError):
            raise ValidationError('%s is not a valid value' % value)


class UnixEpochDateField(serializers.DateField):

    def to_representation(self, value):
        return self.date_to_epoch(value)

    def to_internal_value(self, value):
        return self.epoch_to_date(value)

    @staticmethod
    def date_to_epoch(value):
        try:
            return int(calendar.timegm(value.timetuple()))
        except (AttributeError, TypeError):
            return None

    @staticmethod
    def epoch_to_date(value):
        try:
            return datetime.date.fromtimestamp(int(value))
        except (ValueError, TypeError):
            raise ValidationError('%s is not a valid value' % value)


#Then lets say you want to serialize an example model with date_created in unix epoch, here is how you would do it:
#utils/your-django-project/example-app/serializers.py
from utils.serializers import UnixEpochDateTimeField
from .models import Example
class ExampleSerializer(serializers.ModelSerializer):
  date_created = UnixEpochDateTimeField()
  class Meta:
    model = Example
    fields = '__all__'