The projector on my atomic clock is displaying incomplete data

To correct the time on your Sharp Atomic clock, you will need to reset the time zone. To do this, press and hold the "Time Zone" button for 3 seconds until the time zone flashes. Then, press the "Hour" and "Minute" buttons to adjust the time zone to the correct time zone. Once the time zone is set, press the "Time Zone" button again to save the settings. The clock should now be displaying the correct time.

https://mb.nawcc.org/threads/setting-a-centrios-atomic-clock.32197/
If the atomic radio controlled clock is off by one or more hours, it probably has to do with the time zone setting. ... Other atomic wall clocks may allow the selection of any time zone, even time zones that are outside the WWVB coverage area. When purchasing a clock, make sure that it can display the correct time zone. https://www.weathershack.com/static/ed-atomic-clock-synch.html

I know this is old, but just press the set button. Don't hold it down, just press it once.

Hi Susuan,
One of these methods below should get your device working properly. Good luck!
LaCorosse Tech Support email address.
The product information page
From the manual:
915MHz RECEPTION CHECK FOR OUTDOOR TEMPERATURE SENSOR
The atomic clock will receive the temperature data within 3 minutes. If the temperature data is not being received 3 minutes after setting up (the display shows "- - -"), then please check the following points:
1. The distance of the atomic clock or outdoor temperature sensor should be at least 6 feet (2meters) away from any interfering sources such as computer monitors or TV sets.
2. Avoid placing the receiver onto or in the immediate proximity of metal window frames.
3. Using other electrical products such as headphones or speakers operating on the same signal frequency (915MHz) may prevent correct signal transmission and reception.
4. Neighbors using electrical devices operating on the 915MHz signal frequency can also cause interference.
Note:
When the 915 MHz signal is received correctly, do not re-open the battery cover of either the outdoor temperature sensor or atomic clock, as the batteries may spring free from the contacts and force a false reset. Should this happen accidentally then reset all units (see Setting up above) otherwise transmission problems may occur.
The maximum transmission range is 330 feet (100 meters) from the outdoor temperature sensor to the atomic clock (in open space). However, this depends on the surrounding environment and interference levels. If no reception is possible despite the observation of these factors, all system units have to be reset (see Setting up).

Place your Seth Thomas atomic clock face-down on a table or desk and locate a series of buttons labeled "PST," "MST," "CST" and "EST" on the back of the clock. Press the appropriate button to set the time zone.

2

Turn your attention to the small lithium battery-powered digital clock display on the back of your clock. With the correct time zone set, the digital display should accurately reflect the current local time.

3

Locate the AA battery compartment on the back of your clock. Put two new AA batteries into your clock's battery compartment.

4

Set the "Mode" switch on the back of your Seth Thomas atomic clock to "Run." Wait for it to adjust to the correct time. The automatic time-adjustment process can take up to 45 minutes, but is usually completed much sooner.

Read more: How to Set a Seth Thomas Atomic Clock ' eHow.com http://www.ehow.com/how_6120534_set-seth-thomas-atomic-clock.html#ixzz1GyAcVHP2 hope this helps you

Check out this answer:
http://www.fixya.com/support/t3486802-set_clock

Batteries must come out of both the temperature sensor (transmitter) and base (clock and temperature display). Leave out for about 4 minutes. Replace the batteries in the temperature sensor FIRST and set it about 5 - 10 feet away from the base. Replace the batteries in the base and leave them both set without touching any buttons for at least 15 minutes (usually only takes 5 minutes or so). The temperature should start to display. You can set the clock manually to the correct time and have it get the updates via radio in the evening or night. Should work after all this just fine. (have done it alot of times this way over the years)

Good luck.

You didn't tell us the model number but whatever it is, you should find instructions here:
Skyscan website
Our various 'atomic' clocks have either a menu that lets one select or a simple slide switch with US time zones from which to choose. 

Online manual is at link http://skyscan.info/content/manuals/25-model-87315.html

Just did this after problem resetting after changing batteries, press setover and again til it displays est, then press+until your time zone is displayed, it will also display dst, press +till on/or off depending on your location, then US will appear, clock will then set itself. Good luck, how frustrating.