Why do I have Calendar Date Dimension in my Logical Layer?

Question

If I look in my logical layer and then looking at the models, each of my Fact tables have their corresponding dates such as Order Date, Date Updated, Date Shipped etc.  This is OK. But each single Fact, I see a Calendar Date which is a duplicate of another date dimension.  What I mean if I look in Fact A, I will have Date Transaction, Date Shipped, Date Ordered and Date Calendar.  Date Calendar has the same join relationship as Date Shipped.    Another Fact table Date Calendar has a same relationship as Date Transaction.
Is this a common modelling practice, is this only used for ease of use for business end users?  Do you know why would would do this and what the benefit is?
Thank you!

Answer 1

Thanks for your replies,  I understand the Alias concept.  Let me write it a different way.
Dim_Date = Physical Table
W_DATE_ORDERED_D, W_DATE_SHIPPED_D, W_DATE_TRANSACTION_D and W_DATE_UPDATED_D are all alias that come from my DIM_DATE Physical Table.   Each of these Aliases are joined to my fact tables.
FACTTABLE1.ORDERDATEID joined to W_DATE_ORDERED_D.DATEID AND FACTTABLE1.SHIPPEDDATEID joined to W_DATE_SHIPPED_D.DATEID
FACTTABLE2.TRANSACTIONDATEID joined to W_DATE_TRANSACTION_D.DATEID AND FACTTABLE2.UPDATEDDATEID joined to W_DATE_UPDATED_D.DATEID
The above part I understand fully,  what I also have is this:
FACTTABLE1.ORDERDATEID joined to W_DATE_CALENDAR_D.DATEID
and
FACTTABLE2.TRANSACTIONDATEID joined to W_DATE_CALENDAR_D.DATEID
Documentation states that calendar dates are used more for business logical reasons for the end users, and that the Calendar dates joined to the fact date ids, the fact date ids are the more commonly used dates for reporting.
Does that make sense?
Thank you