Q:

I change when to where - another riddle

I managed to write a rhyming one this time! 
I sound like a sieve, 
But knowledge I give.  
I change when to where; 
Just find the right square. 
A cycle moves me to the right, 
But never entirely out of sight.  
Seven by four, or usually more, 
Betwixt the ceiling and the floor. 
What am I? 

A:

Sounds like it could be a

Calendar

I sound like a sieve

 Maybe a sieve is a grid

But knowledge I give

 Calendar can be an external brain for keeping track of everything

I change when to where

 As an appointment time approaches, it will tell you where you need to be

A cycle moves me to the right
But never entirely out of sight

 A cycle of days is a month and as months increase, they normally show a smaller version of the prior and next month.  As we imagine a year goes left to right, this may indicate direction. 

Seven by four or usually more

 28 days in Feb, otherwise 29, 30 or 31

Betwixt the ceiling and the floor

Hangs on the wall. 

From the comments on where I was a little off - 

  A "sieve" is like a colander, which sounds like calendar. " When to
  where" is supposed to mean that 'which day?'  when you're looking on a
  calendar becomes a spatial question rather than a temporal one.  A
  "cycle" is supposed to mean a day; as each day passes (unless it's the
 end of the week) you move one square to the right on the calendar. –  
 rand al'thor

A:

 The blackboard

I sound like a sieve, 

 For the sound of the chalk

But knowledge I give.  

 I'm used for teaching

I change when to where;
Just find the right square. 

 The tool to wipe

A cycle moves me to the right, 
But never entirely out of sight.  

 Less clear to me, but perhaps it refers to those that can be swapped

Seven by four, or usually more, 

 Feet? 

Betwixt the ceiling and the floor

 Usually hanging on the wall

