Models

If you want to access from Study the events, it's recommendable to add a generic relation

from django.db import models
from django.contrib.contenttypes import generic
from events.models import Event

class Study(models.Model):
    ...
    events = generic.GenericRelation(Event)
    ...

API

Get the events related to a Study:

study = Study.objects.get(pk=1)
study.events.all()

Add an event to a Study:

from events.models import Event
from datetime import date, time

study = Study.objects.get(pk=1)
event = Event(date.today(), time.now())

event.related_object = study
event.save()

study.events.get(pk=event.pk)

Play with the occurrences of an event:

from events.models import Event

event = Event.objects.get(pk=1)

#get all the occurrences as an iter of datetimes
event.get_occurrences()

#get all of past occurrences as a list of datetimes
event.get_past_occurrences()

#get the last 20 past occurrences as a list of datetimes
event.get_past_occurrences(20)

#get the next 20 future occurrences as a list of datetimes
event.get_future_occurrences(20)

#update the Occurrence objects of an event
event.update_occurrences(event.get_occurrences)

#get the Occurrence objects of an event
event.occurrence_set.all()

#get all the Study objects that have occurrences in the future
from datetime import datetime
Study.objects.filter(events__occurrence__datetime__gt=datetime.now())

Admin

If, when you are editing a Study in admin, you want to also edit the related events, you are easilly done:

from django.contrib import admin

from events.admin import EventInline

class StudyAdmin(admin.ModelAdmin):
    ...
    inlines = EventInline,
    ...
admin.site.register(Study, StudyAdmin)

Forms

You can also use the event form:

from events.forms import EventForm