Earth&Sun for Palm OS: Sunlight, Sunrise and World-Time Calculations on PalmPilot

During the Palm OS era, PalmGear.com catalogued thousands of small utilities written by independent developers, and one of the more specialized entries was Earth&Sun, a program for the original PalmPilot and its successors that drew the sunlit half of the Earth on the device's grayscale or color screen and paired that visualization with a set of location, time, and solar calculations. PalmGear listed the program under product ID 4462, a number preserved today mainly because a contemporary astronomy writer linked to it directly in a December 2002 software roundup. This restored page documents what can actually be verified about Earth&Sun from surviving sources — and is equally explicit about what cannot be confirmed, since the developer's own site is no longer reachable and no cached copy of it could be located during this research.

Earth&Sun was not a simulator or a game; it belonged to the small category of Palm OS "world clock plus almanac" utilities that briefly flourished when the PalmPilot became a common accessory for travelers, radio operators, and amateur astronomers who wanted quick sun-position and time-zone answers without carrying a separate reference book. This article treats it strictly as historical, discontinued software — it has not been maintained for over two decades, and this page is a factual record, not a download offer or an active support resource.

What Was Earth&Sun for Palm OS?

The clearest surviving description of Earth&Sun comes from a "Computers in Astronomy" column written by amateur astronomer Don Shedrick, dated November 22, 2002, and archived on a University of Delaware faculty page. Shedrick reviewed a batch of Palm OS astronomy software pulled from PalmGear's astronomy category listing, and his entry for Earth&Sun reads, in full:

"Earth&Sun is a program for the PalmPilot to show the Sun Illuminated area of the Earth. It will also display: The latitude and longitude of an Earth location; the time zone at that location, based on only longitude, not civil boundaries; the current time at that location based on the above time zone; the sunrise, sunset times, and day length at that location; the great circle distance between two locations on the earth."

That single paragraph is the most complete period description of the program located during this research. It confirms the program combined two distinct things in one package: a graphical day/night map of the Earth, and a set of numeric almanac-style calculations (location, time, sunrise/sunset, distance) tied to that map. No separate marketing copy, user manual, or developer README for Earth&Sun was found to expand on this description, so this restored page treats Shedrick's write-up as the primary source for the program's feature list.

The Sunlit Earth Display

The headline feature — showing "the Sun Illuminated area of the Earth" — describes what is often called a day/night map: a flat or globe-style rendering of the planet with a shaded band marking the region currently in darkness, moving continuously as the Earth rotates and as the seasons shift the terminator's tilt. This is the same underlying concept used by better-documented contemporaries such as the desktop program DayNight or the "World Time" globe views bundled with some Palm OS world-clock utilities, though no source located here specifies whether Earth&Sun used a flat equirectangular map, a rotating globe, or some other projection. Absent a surviving screenshot or manual, this article does not guess at the exact rendering style Earth&Sun used — only that its stated purpose was to visualize which half of the planet was currently lit by the Sun.

On a monochrome or 160×160 color PalmPilot-class screen, a day/night map like this would have been a compact, glanceable way to answer a practical question travelers and radio operators frequently had in that era: is it daytime or nighttime right now at the other location I care about, without doing the math by hand.

Sunrise, Sunset, and Day Length

Beyond the map, Earth&Sun calculated sunrise time, sunset time, and total day length for a given Earth location, according to the Shedrick description. These are standard outputs of a solar-position/almanac calculation once a location's latitude, longitude, and date are known. No source located during this research documents which specific sunrise/sunset algorithm Earth&Sun used (for example, whether it accounted for atmospheric refraction or used a simple geometric horizon), what precision its latitude/longitude entry supported, or how locations were entered or stored — whether from a built-in city database, manual coordinate entry, or both. The "user-entered locations" capability that might be expected of a program like this is plausible but was not directly confirmed by any surviving source, so it is not asserted here as fact.

Longitude-Based Time Zones: A Documented Limitation

This is the one technical limitation of Earth&Sun that is explicitly documented in the historical record, rather than inferred. Shedrick's 2002 write-up specifically calls out that the program's time zone for a given location was "based on only longitude, not civil boundaries" — meaning the software estimated a location's offset from a reference time purely by dividing its longitude by 15 degrees (the width of one idealized time zone), rather than by looking up which actual, government-defined time zone that location falls in.

Note: Real-world civil time zones almost never line up cleanly with longitude. National borders, provincial boundaries, and political decisions routinely bend time zones far from their "natural" longitudinal band — China observes a single time zone across a longitudinal span that would normally cover five, parts of Western Europe sit in Central European Time despite being west of the Greenwich meridian, and countless regions apply local exceptions, half-hour offsets, or seasonal daylight-saving shifts that a pure longitude calculation cannot know about. A program computing time zone strictly from longitude — as the 2002 source states Earth&Sun did — will therefore often show a time that differs, sometimes by an hour or more, from the official clock time actually in use at that location. This was a documented characteristic of the software, not a defect unique to it; several period longitude-based "world time" utilities shared the same simplification because building and maintaining a true civil time-zone and daylight-saving database was a substantially larger undertaking.

No source located during this research states whether Earth&Sun made any attempt to adjust for daylight saving time. Given that its time zone model was longitude-based rather than tied to real jurisdictions, and that DST rules are themselves a civil/political construct rather than a geographic one, it is plausible the program did not apply DST adjustments — but this is not confirmed, and this article does not assert it as fact.

Great-Circle Distance Between Locations

The fourth calculation Shedrick documents is the great-circle distance between two Earth locations. A great-circle distance is the shortest path between two points measured along the surface of a sphere (as opposed to a straight line drawn on a flat map, which is not the shortest real-world path once distances get large) — it is the calculation behind how commercial flight paths are plotted and how "as the crow flies" distances between distant cities are properly computed. For a program already built around a spherical Earth model and a location database, adding a great-circle distance calculator between any two stored or entered points was a natural extension, and it is consistent with the kind of two-location comparison tools (distance, time difference, day/night status) that period Palm world-clock software commonly offered. No source located here documents which formula (e.g., the spherical law of cosines or the haversine formula) Earth&Sun used internally, nor its distance-unit options (miles vs. kilometers) or claimed precision.

Who Likely Used Earth&Sun

No developer statement, advertisement, or review located during this research explicitly names an intended audience for Earth&Sun. Based only on the confirmed feature set — a day/night world map, sunrise/sunset/day-length for a location, an approximate time-zone/current-time readout, and point-to-point great-circle distance — the program's practical uses can be reasonably described without overstating developer intent: travelers and business users wanting a rough sense of local time and daylight status at a distant location; outdoor and amateur-astronomy users who wanted sunrise/sunset times for a location without a separate almanac; and radio operators, for whom knowing which parts of the globe are in daylight versus darkness has a real practical bearing on shortwave propagation conditions. These are plausible use cases given the feature set, not developer-confirmed audiences, and they are presented here as inference rather than sourced fact.

Earth&Sun and RiseSet: A Shared Developer Site

The same 2002 astronomy column that documents Earth&Sun also reviews a second, related Palm OS program called RiseSet (PalmGear product ID 4463 — the number immediately following Earth&Sun's 4462), which computed rise, transit, and set times for the Sun and Moon, altitude/azimuth angles, twilight times, and lunar eclipse information. Shedrick's column explicitly credits RiseSet to "developer David Bray" and gives its download location as http://www.40-below.com/palm/, with documentation at http://www.40-below.com/palm/riseset.html. Earth&Sun's own download link in the same column — http://www.40-below.com/palm/earth&sun.html — lives in that identical directory on the identical domain.

This is meaningful circumstantial evidence that Earth&Sun and RiseSet shared a common host, and quite possibly a common author, since both programs' download pages sat side-by-side under the same developer's /palm/ folder on 40-below.com and both were being distributed together as of late 2002. However, the Shedrick column — the only source located that names a developer for either program — credits David Bray by name specifically to RiseSet, and does not explicitly state that Bray also wrote Earth&Sun. No independent source confirming Earth&Sun's author was found. This article therefore reports the shared-hosting fact plainly while stopping short of asserting shared authorship as confirmed.

Further corroborating the pairing, a personal Palm software page maintained by a Rutgers University computer science affiliate (see next section) separately lists both "Earth & Sun 1.2" and "RiseSet 1.3" among the programs installed on the same Palm IIIx handheld — consistent with the two being commonly downloaded together from the same developer site during the same period, though again this does not by itself prove common authorship.

Version History: What We Know About 1.2

The only version number for Earth&Sun confirmed by a surviving source is 1.2. It appears on a personal "Palm software" reference page maintained by a Rutgers University-affiliated computer scientist, which lists software the page's author had installed on a Palm IIIx handheld, including the line "Earth & Sun 1.2" linked to http://cold.40-below.com/palm/earth&sun.html (a cold. subdomain variant of the same 40-below.com developer site referenced in the 2002 astronomy column). That page does not give an install date or release date for version 1.2 specifically, and its own "last updated" note refers to general page maintenance rather than to when Earth&Sun 1.2 was installed or released.

No source located during this research documents a version 1.0 or 1.1 release, a changelog describing what changed in 1.2, or any version released after 1.2. It cannot be confirmed whether 1.2 was Earth&Sun's final release or simply the last version that happened to be referenced in surviving pages. Readers should treat "1.2" as the latest version documented by surviving evidence, not as a confirmed final release.

Palm OS Compatibility and Technical Specs

Confirmed hardware/software compatibility is limited to what can be directly evidenced: Earth&Sun 1.2 is documented as having been installed and used on a Palm IIIx, a monochrome Palm OS 3.x-era device, per the Rutgers-affiliated software page. Its listing in a late-2002 PalmGear astronomy roundup indicates it was still being actively distributed at a time when Palm OS 4 and early Palm OS 5 devices were current on the market, but no source located here states explicit minimum OS requirements, color-screen support, high-density-display support, or compatibility with specific later devices (Palm V, Palm m100 series, Tungsten, Zire, etc.). The table below separates what is confirmed from what is unknown, rather than presenting estimated compatibility as fact.

The PalmGear Listing and Product ID 4462

Earth&Sun's PalmGear catalog entry is preserved only as a URL cited in the 2002 astronomy column, not as an archived page with its own surviving content: http://palmgear.com/software/showsoftware.cfm?sid=54905620021122082656&prodID=4462. The prodID=4462 parameter is the stable identifier this restored page is built around, and it was cross-checked directly against the source article's text (rather than taken from a search-engine summary, several of which incorrectly conflated it with the neighboring RiseSet listing, prodID 4463) to confirm it unambiguously refers to Earth&Sun. The column also references PalmGear's astronomy-category browse page, http://palmgear.com/software/answer_category.cfm?categoryIDs=157, as the starting point from which the reviewer found Earth&Sun and the other programs covered in the same piece. No cached or archived copy of the actual PalmGear product page for 4462 (with its original description text, price, file size, screenshots, or user ratings) was located during this research.

The palmgear.com domain today hosts an unrelated, present-day gadget review site (the site this article is published on) rather than the historical Palm software catalog; the original PalmGear software store closed years ago, and its historical listings are not accessible at the live domain.

Availability Today

The developer site referenced by both the 2002 astronomy column (www.40-below.com) and the Rutgers-affiliated page's cold. subdomain variant did not respond during research for this article, consistent with a long-defunct domain. No working download link, archived installer file, or currently maintained mirror for Earth&Sun was located. Readers should assume the program is not available through any official or legitimately licensed channel today; this restored page exists to document the software's history, not to offer or point to a download.

What We Could Not Verify

In keeping with this being a historical accuracy-first restoration rather than promotional content, the following specific points could not be confirmed by any source located during research, and are explicitly flagged rather than assumed:

• The individual developer or company name behind Earth&Sun specifically (only RiseSet, hosted at the same domain, is explicitly credited to David Bray in the sole source found).
• The original release date of Earth&Sun or of version 1.2 specifically.
• Whether any version newer than 1.2 was ever released.
• Minimum Palm OS version required, and compatibility with Palm OS 4 or 5 devices.
• Map projection or rendering style used for the sunlit-Earth display.
• Whether locations came from a built-in database, free-form user entry, or both.
• The sunrise/sunset calculation method and its accounted-for factors (e.g., atmospheric refraction).
• The great-circle distance formula used and its supported distance units.
• Whether daylight saving time was factored into the displayed local time.
• Latitude/longitude entry precision.
• File size, price, and freeware/shareware licensing status.
• Any surviving screenshots, user manual, or developer documentation beyond the single third-party description discussed above.

Frequently Asked Questions

Key Takeaways

• Earth&Sun was a Palm OS utility that displayed the sunlit half of the Earth and calculated location latitude/longitude, an approximate time zone, current time, sunrise, sunset, day length, and great-circle distance between two locations.
• PalmGear catalogued it under product ID 4462, verified via a direct URL citation in a November 22, 2002 "Computers in Astronomy" column by Don Shedrick.
• Its time zone calculation was explicitly documented as longitude-based rather than tied to real civil/political time-zone boundaries, meaning displayed local time could diverge from official clock time.
• Version 1.2 is the only confirmed version, documented as installed on a Palm IIIx via a Rutgers-affiliated personal Palm software page.
• Earth&Sun was distributed from the same 40-below.com developer domain and directory as RiseSet (PalmGear prodID 4463), which is explicitly credited to developer David Bray — a shared-hosting connection, though not confirmed shared authorship.
• Developer name, exact release dates, price/licensing, file size, OS compatibility beyond the Palm IIIx, and the underlying sunrise/sunset and distance formulas could not be verified from any source located during this research.
• The original developer site is no longer reachable, and no legitimate current download source for Earth&Sun was found.