Set Up

Just a simple example initialized with the gsm.utils::MakeExample function.

Setup 
# Compute lunar phase offline (no external APIs)
moon_phase <- function(date = Sys.Date()) {
    year <- as.integer(format(date, "%Y"))
    month <- as.integer(format(date, "%m"))
    day <- as.integer(format(date, "%d"))

    if (month < 3) {
        year <- year - 1L
        month <- month + 12L
    }

    month <- month + 1L
    c_val <- 365.25 * year
    e_val <- 30.6 * month
    jd <- c_val + e_val + day - 694039.09
    jd <- jd / 29.5305882
    phase <- jd - floor(jd)
    age <- phase * 29.5305882

    phase_name <- if (age < 1.84566) {
        "New Moon"
    } else if (age < 5.53699) {
        "Waxing Crescent"
    } else if (age < 9.22831) {
        "First Quarter"
    } else if (age < 12.91963) {
        "Waxing Gibbous"
    } else if (age < 16.61096) {
        "Full Moon"
    } else if (age < 20.30228) {
        "Waning Gibbous"
    } else if (age < 23.99361) {
        "Last Quarter"
    } else if (age < 27.68493) {
        "Waning Crescent"
    } else {
        "New Moon"
    }

    emoji <- switch(
        phase_name,
        "New Moon" = "🌑",
        "Waxing Crescent" = "🌒",
        "First Quarter" = "🌓",
        "Waxing Gibbous" = "🌔",
        "Full Moon" = "🌕",
        "Waning Gibbous" = "🌖",
        "Last Quarter" = "🌗",
        "Waning Crescent" = "🌘",
        "🌑"
    )

    list(age_days = age, phase = phase_name, emoji = emoji)
}

moon_info <- moon_phase(Sys.Date())

Report

message(
    "Goodnight, moon! In Durham, NC (offline estimate), today is a ",
    moon_info$phase,
    " ",
    moon_info$emoji,
    " (lunar age ~ ",
    sprintf("%.1f", moon_info$age_days),
    " days). Rendered on ",
    Sys.time()
)
## Goodnight, moon! In Durham, NC (offline estimate), today is a Waxing Gibbous 🌔 (lunar age ~ 12.4 days). Rendered on 2026-01-30 20:13:32.050321