Okay, now this makes sense as to why you want to do it.

Using the sample code you provided, I created this test:

if object_id('tempdb..#Dates') is not null DROP TABLE #Dates

CREATE TABLE #Dates (DateField datetime)

insert into #Dates

select '1900-01-30 00:00:00.000' union all

select '1900-01-30 00:00:00.000' union all

select '1900-03-04 00:00:00.000' union all

select '1901-11-09 00:00:00.000' union all

select '1901-11-09 00:00:00.000'

select DateField, convert(int, DateField) from #Dates

As you can see, just converting the field to an int is giving you the desired results.

Based on this, you would think that you could just do this:

ALTER TABLE "tablename" ALTER COLUMN "columnname" INTEGER

if you try this, you will get this error:

So, you will have to add a new field to your table, populate it with the integer representation of your date field, and finally dropping the date field. My final code for showing all of this is:

if object_id('tempdb..#Dates') is not null DROP TABLE #Dates

CREATE TABLE #Dates (DateField datetime)

insert into #Dates

select '1900-01-30 00:00:00.000' union all

select '1900-01-30 00:00:00.000' union all

select '1900-03-04 00:00:00.000' union all

select '1901-11-09 00:00:00.000' union all

select '1901-11-09 00:00:00.000'

select DateField, convert(int, DateField) from #Dates

GO

alter table #Dates add NewDateField INT

GO

update #Dates set NewDateField = convert(int, DateField)

select * from #Dates

GO

alter table #Dates DROP COLUMN DateField

GO

select * from #Dates

Of course, MAKE SURE that you try this out IN A TEST ENVIRONMENT. As "the keeper of the data", your first priority is retaining that accurate data that you do have. Only do this in production when you are sure you will get what you want.