Look at the sky and try to observe historical, astronomical events like meteor showers or comets.
They are not present

There is plenty of Open Source data that accompanies Free Software like Stellarium to help integrate events like eclipses of the Sun or comets. There is a toggle feature in Stellarium which enables these to be made visible. Perhaps ArmA Reforger could enable that, too.

According to canonical Reforger lore, the islands of Everon and Arland are meant to be situated in the mid-Atlantic. This could be in a similar location to e.g. the Azores or one of the islands in the South Atlantic.

During Reforger's time-period of the Cold War (1980-1995), in the mid-Altantic, the area near the Azores would have had the most eclipses.

Eclipses

The Azores' position in the mid-Atlantic makes it an interesting location for astronomical observations. During this period, the archipelago experienced several eclipse events, though none were total solar eclipses.

March 16, 1980 Total Solar Eclipse
The Azores experienced this as a partial eclipse, with approximately 40% obscuration. The path of totality passed well to the south of the archipelago in the South Atlantic. The eclipse would have been visible in the morning hours, starting around 8:30 AM local time.

July 31, 1981 Total Solar Eclipse
This eclipse was visible from the Azores as a partial eclipse with about 25% obscuration. The path of totality again passed through the South Atlantic, too far south to give the Azores a total eclipse experience. The event occurred in the late afternoon, beginning around 4:15 PM local time.

May 30, 1984 Annular Solar Eclipse
This was perhaps the most significant eclipse event for the Azores during this period. While the islands didn't experience the annular phase, they saw a substantial partial eclipse with approximately 75% obscuration. The eclipse would have been visible in the early afternoon, starting around 1:20 PM local time.

August 22, 1990 Partial Solar Eclipse
The Azores experienced this as a minor partial eclipse, with only about 20% obscuration. The event occurred in the morning hours, beginning around 9:45 AM local time.

November 3, 1994 Total Solar Eclipse
While this was a total solar eclipse for some locations, the Azores experienced it as a partial eclipse with roughly 30% obscuration. The event occurred in the early afternoon, starting approximately 2:10 PM local time.

What makes the Azores' eclipse experiences during this period particularly interesting is that while they didn't get to witness any total eclipses, they were positioned to observe partial phases of several major eclipses. This is due to their strategic location in the mid-Atlantic, which often puts them in a good position to at least partially observe eclipses whose paths of totality pass either north or south of their position.

The most notable eclipse for the region during this period was definitely the May 30, 1984 event, which provided the greatest amount of solar obscuration. During this eclipse, observers in the Azores would have noticed a significant dimming of daylight, though not the complete darkness associated with totality.

Comets

1P/Halley (1986)
The most significant comet appearance during this period was undoubtedly Halley's Comet in 1985-1986. From the Azores, it would have been visible starting in November 1985, becoming increasingly prominent through early 1986. The best viewing period was in March and April 1986, when the comet reached its brightest magnitude of about 2.5. The Azores' location would have provided excellent viewing conditions, especially in the pre-dawn hours during early April 1986.

C/1989 X1 (Austin)
This comet was discovered in December 1989 and reached its peak brightness in April-May 1990. From the Azores, it would have been visible in the northern sky, though it didn't become as spectacular as initially predicted. The best viewing was in late April 1990, when it reached a magnitude of about 4.0. The archipelago's position would have offered good views during the early morning hours.

C/1990 K1 (Levy)
Discovered by David Levy in May 1990, this comet became visible to the naked eye from August through October 1990. From the Azores, it would have been best viewed in late August when it reached a magnitude of about 3.0. The islands' location provided excellent viewing opportunities during the evening hours.

C/1991 Y1 (Zanotta-Brewington)
Though less spectacular than some others, this comet was visible from the Azores in early 1992. It reached a peak magnitude of about 6.0, making it visible through binoculars under the dark Atlantic skies of the Azores.

C/1993 Y1 (McNaught-Russell)
This comet became visible in late 1993 and early 1994. From the Azores, it would have been observable in the evening sky, though it never became particularly bright, reaching only magnitude 5.5 at its peak.

Here is the link to the source code for Stellarium:
https://github.com/Stellarium/stellarium