# models.py
class DateSum(models.Model):
    category = models.ForeignKey(CategoryReport, on_delete=models.CASCADE)
    total = models.DecimalField(max_digits=22, decimal_places=6)
    report_date = models.ForeignKey(ReportDate, on_delete=models.CASCADE, related_name="reportdate_related")

# admins.py
class DateSumAdmin(admin.ModelAdmin):
    ordering = ("reportdate_related__dt", )