day-27-boundaries.R

# Day 27: Boundaries - World Time Zones
# The invisible lines that govern our daily lives
# Uses current IANA time zone rules, including daylight saving time at render time.

library(mapgl)
library(sf)
library(dplyr)
library(lubridate)

tz_release <- "2026b"
# "now" is lighter and groups places by current/future clock behavior.
# Use "1970" if you want the finer historical IANA zones, like Indiana's legacy intricacies.
tz_scope <- "now"
# Xinjiang has overlapping official China time (UTC+8) and local Urumqi time (UTC+6) usage.
# Use "dual" to show both in the popup, "official" for Beijing/China Standard Time,
# "local" for Urumqi/Xinjiang Time, or "both" to preserve the source overlap.
xinjiang_policy <- "dual"
tz_url <- paste0(
  "https://github.com/evansiroky/timezone-boundary-builder/releases/download/",
  tz_release,
  "/timezones-with-oceans-",
  tz_scope,
  ".geojson.zip"
)

utc_now <- with_tz(Sys.time(), "UTC")
user_tz <- Sys.timezone()
user_time <- with_tz(utc_now, user_tz)

read_timezone_boundaries <- function(url) {
  temp_zip <- tempfile(fileext = ".zip")
  temp_dir <- tempfile("timezone-boundaries-")
  dir.create(temp_dir)
  on.exit(unlink(c(temp_zip, temp_dir), recursive = TRUE), add = TRUE)

  download.file(url, temp_zip, mode = "wb", quiet = TRUE)
  unzip(temp_zip, exdir = temp_dir)

  geojson <- list.files(temp_dir, pattern = "\\.json$", full.names = TRUE)
  if (length(geojson) != 1) {
    stop("Expected exactly one GeoJSON file in timezone boundary archive.")
  }

  st_read(geojson, quiet = TRUE)
}

offset_minutes <- function(time, tz) {
  if (is.na(tz) || !tz %in% OlsonNames()) {
    return(NA_integer_)
  }

  offset <- format(time, tz = tz, format = "%z")
  sign <- ifelse(substr(offset, 1, 1) == "-", -1L, 1L)
  hours <- as.integer(substr(offset, 2, 3))
  minutes <- as.integer(substr(offset, 4, 5))

  sign * (hours * 60L + minutes)
}

offset_label <- function(minutes) {
  if (is.na(minutes)) {
    return("UTC unknown")
  }
  if (minutes == 0) {
    return("UTC")
  }

  sign <- ifelse(minutes > 0, "+", "-")
  abs_minutes <- abs(minutes)
  hours <- abs_minutes %/% 60L
  mins <- abs_minutes %% 60L

  if (mins == 0) {
    paste0("UTC", sign, hours)
  } else {
    paste0("UTC", sign, hours, ":", sprintf("%02d", mins))
  }
}

format_time_in_tz <- function(time, tz, format) {
  if (is.na(tz) || !tz %in% OlsonNames()) {
    return(NA_character_)
  }

  format(time, tz = tz, format = format)
}

resolve_xinjiang_overlap <- function(zones, policy = c("dual", "official", "local", "both")) {
  policy <- match.arg(policy)
  zones$alternate_tzid <- NA_character_
  zones$zone_label_override <- NA_character_
  zones$zone_note <- NA_character_

  if (policy == "both") {
    return(zones)
  }

  # In the "now" file, Asia/Manila represents current UTC+8 behavior, including China.
  # Asia/Dhaka represents current UTC+6 behavior, including local Xinjiang/Urumqi time.
  official_tz <- "Asia/Manila"
  local_tz <- "Asia/Dhaka"
  if (!all(c(official_tz, local_tz) %in% zones$tzid)) {
    return(zones)
  }

  old_s2 <- sf_use_s2()
  on.exit(suppressMessages(sf_use_s2(old_s2)), add = TRUE)
  suppressMessages(sf_use_s2(FALSE))

  zones <- st_make_valid(zones)
  official_idx <- which(zones$tzid == official_tz)
  local_idx <- which(zones$tzid == local_tz)
  zones_work <- st_make_valid(st_transform(zones, 6933))

  overlap <- suppressMessages(suppressWarnings(st_intersection(
    st_geometry(zones_work[official_idx, ]),
    st_geometry(zones_work[local_idx, ])
  )))

  if (length(overlap) == 0) {
    return(zones)
  }

  overlap <- suppressMessages(suppressWarnings(
    st_collection_extract(st_make_valid(st_union(overlap)), "POLYGON")
  ))
  xinjiang_extent <- st_as_sfc(st_bbox(
    c(xmin = 73, ymin = 34, xmax = 97, ymax = 50),
    crs = st_crs(zones)
  ))
  xinjiang_extent <- st_transform(xinjiang_extent, st_crs(zones_work))
  overlap <- suppressMessages(suppressWarnings(st_intersection(overlap, xinjiang_extent)))

  trim_zone <- function(zone_idx) {
    trimmed <- suppressMessages(suppressWarnings(st_difference(st_geometry(zones_work[zone_idx, ]), overlap)))
    trimmed <- suppressMessages(suppressWarnings(st_collection_extract(st_make_valid(trimmed), "POLYGON")))
    trimmed <- suppressMessages(suppressWarnings(st_transform(st_union(trimmed), st_crs(zones))))
    st_geometry(zones)[zone_idx] <<- trimmed
  }

  if (policy == "official") {
    trim_zone(local_idx)
    return(zones)
  }

  if (policy == "local") {
    trim_zone(official_idx)
    return(zones)
  }

  xinjiang <- zones[official_idx, ]
  st_geometry(xinjiang) <- suppressMessages(suppressWarnings(st_transform(st_union(overlap), st_crs(zones))))
  xinjiang$alternate_tzid <- local_tz
  xinjiang$zone_label_override <- "Xinjiang / Urumqi"
  xinjiang$zone_note <- "Official China time and local Urumqi time are both shown."
  zones <- rbind(zones, xinjiang)
  zones
}

timezones <- read_timezone_boundaries(tz_url)
timezones <- resolve_xinjiang_overlap(timezones, xinjiang_policy)

valid_tz <- timezones$tzid %in% OlsonNames()
if (any(!valid_tz)) {
  warning(
    "Some boundary time zone IDs are not available in this R/system tz database: ",
    paste(timezones$tzid[!valid_tz], collapse = ", ")
  )
}

timezones <- timezones |>
  mutate(
    offset_minutes = vapply(tzid, function(tz) offset_minutes(utc_now, tz), integer(1)),
    utc_offset = offset_minutes / 60,
    current_time = vapply(tzid, function(tz) format_time_in_tz(utc_now, tz, "%H:%M"), character(1)),
    time_ampm = vapply(tzid, function(tz) format_time_in_tz(utc_now, tz, "%I:%M %p"), character(1)),
    date_display = vapply(tzid, function(tz) format_time_in_tz(utc_now, tz, "%b %d"), character(1)),
    zone_abbr = vapply(tzid, function(tz) format_time_in_tz(utc_now, tz, "%Z"), character(1)),
    offset_label = vapply(offset_minutes, offset_label, character(1)),
    tooltip_title = if_else(is.na(current_time), "Time unavailable", current_time),
    alternate_time = vapply(alternate_tzid, function(tz) format_time_in_tz(utc_now, tz, "%H:%M"), character(1)),
    alternate_ampm = vapply(alternate_tzid, function(tz) format_time_in_tz(utc_now, tz, "%I:%M %p"), character(1)),
    alternate_abbr = vapply(alternate_tzid, function(tz) format_time_in_tz(utc_now, tz, "%Z"), character(1)),
    alternate_offset = vapply(
      vapply(alternate_tzid, function(tz) offset_minutes(utc_now, tz), integer(1)),
      offset_label,
      character(1)
    ),
    primary_time_label = if_else(is.na(alternate_tzid), "Local time", "Official China time"),
    alternate_label = if_else(
      is.na(alternate_tzid),
      "",
      paste0(
        "<div style='margin-top: 10px; padding-top: 10px; border-top: 1px solid rgba(255,255,255,0.14);'>",
        "<div style='font-size: 11px; color: #999; text-transform: uppercase; letter-spacing: 0.4px;'>Local Urumqi Time</div>",
        "<div style='font-size: 20px; font-weight: 700; color: #fff;'>",
        alternate_time,
        "</div>",
        "<div style='font-size: 12px; color: #888;'>",
        alternate_ampm,
        " ",
        alternate_abbr,
        " / ",
        alternate_offset,
        "</div>",
        "</div>"
      )
    ),
    note_label = if_else(
      is.na(zone_note),
      "",
      paste0("<div style='font-size: 11px; color: #777; margin-top: 8px; max-width: 220px;'>", zone_note, "</div>")
    ),
    zone_label = coalesce(zone_label_override, gsub("_", " ", tzid)),
    is_user_tz = tzid == user_tz
  )

xinjiang_timezones <- timezones |>
  filter(!is.na(alternate_tzid))

timezones <- timezones |>
  filter(is.na(alternate_tzid))

user_offset_minutes <- offset_minutes(utc_now, user_tz)
user_offset_label <- offset_label(user_offset_minutes)

user_zone <- timezones |>
  filter(is_user_tz)

if (nrow(user_zone) > 0) {
  user_bbox <- st_bbox(user_zone)
  user_center_lon <- mean(c(user_bbox[["xmin"]], user_bbox[["xmax"]]))
  user_center_lat <- mean(c(user_bbox[["ymin"]], user_bbox[["ymax"]]))
  user_center_lat <- max(min(user_center_lat, 55), -55)
} else {
  user_center_lon <- (user_offset_minutes / 60) * 15
  user_center_lat <- 20
}

cat("Your timezone:", user_tz, "\n")
cat("Your current time:", format(user_time, "%Y-%m-%d %H:%M:%S %Z"), "\n")
cat("UTC offset:", user_offset_label, "\n")
cat("Timezone boundary release:", tz_release, "\n")
cat("Timezone boundary scope:", tz_scope, "\n")
cat("Xinjiang policy:", xinjiang_policy, "\n")

# Time zone color palette - dawn to dusk gradient
tz_palette <- c(
  "#1e3a5f", # UTC-12
  "#2d4a6f", # UTC-10
  "#3d5a7f", # UTC-8
  "#5a7a9f", # UTC-6
  "#7a9abf", # UTC-4
  "#9abadf", # UTC-2
  "#f0f4f8", # UTC
  "#ffe4b5", # UTC+2
  "#ffc987", # UTC+4
  "#ffaa5c", # UTC+6
  "#ff8533", # UTC+8
  "#ff5500", # UTC+10
  "#cc3300", # UTC+12
  "#8f2200"  # UTC+14
)

generated_label <- format(user_time, "%b %d, %Y %H:%M %Z")

info_html <- paste0(
  "<div style='font-family: -apple-system, BlinkMacSystemFont, \"Segoe UI\", Roboto, sans-serif; ",
  "background: rgba(20, 20, 30, 0.95); padding: 16px 20px; border-radius: 8px; ",
  "border: 1px solid rgba(255, 255, 255, 0.1); max-width: 330px;'>",
  "<div style='font-size: 18px; font-weight: 700; color: #fff; margin-bottom: 10px;'>",
  "World Time Zones</div>",
  "<div style='background: rgba(255, 200, 100, 0.15); border: 1px solid rgba(255, 200, 100, 0.4); ",
  "border-radius: 6px; padding: 10px 12px; margin-bottom: 12px;'>",
  "<div style='font-size: 11px; color: #ffc864; text-transform: uppercase; letter-spacing: 0.5px;'>Your Time</div>",
  "<div style='font-size: 24px; font-weight: 700; color: #fff;'>",
  format(user_time, "%H:%M"),
  "</div>",
  "<div style='font-size: 12px; color: #aaa;'>",
  user_tz,
  " (",
  user_offset_label,
  ")",
  "</div>",
  "</div>",
  "<div style='font-size: 12px; color: #888; line-height: 1.5;'>",
  "Hover over any zone to see the local time calculated from IANA time zone rules, including daylight saving where applicable.</div>",
  "<div style='font-size: 10px; color: #555; margin-top: 10px; line-height: 1.4;'>",
  "Calculated at ",
  generated_label,
  ". Current-equivalent IANA zones from timezone-boundary-builder ",
  tz_release,
  " / OpenStreetMap. Xinjiang: ",
  case_when(
    xinjiang_policy == "official" ~ "official China time",
    xinjiang_policy == "local" ~ "local Urumqi time",
    xinjiang_policy == "dual" ~ "both official China time and local Urumqi time shown",
    TRUE ~ "source overlap preserved"
  ),
  ".</div>",
  "</div>"
)

maplibre(
  style = carto_style("dark-matter"),
  center = c(user_center_lon, user_center_lat),
  zoom = 2
) |>
  add_fill_layer(
    id = "timezone-fill",
    source = timezones,
    fill_color = interpolate(
      column = "utc_offset",
      values = c(-12, -10, -8, -6, -4, -2, 0, 2, 4, 6, 8, 10, 12, 14),
      stops = tz_palette,
      na_color = "#333333"
    ),
    fill_opacity = 0.72,
    hover_options = list(
      fill_opacity = 0.95
    ),
    tooltip = concat(
      "<div style='background: #1a1a2e; padding: 14px 18px; border-radius: 8px; ",
      "border: 1px solid rgba(255, 255, 255, 0.2); font-family: system-ui;'>",
      "<div style='font-size: 32px; font-weight: 700; color: #fff;'>",
      get_column("tooltip_title"),
      "</div>",
      "<div style='font-size: 13px; color: #888; margin-bottom: 8px;'>",
      get_column("primary_time_label"),
      ": ",
      get_column("time_ampm"),
      " ",
      get_column("zone_abbr"),
      "</div>",
      "<div style='font-size: 13px; color: #aaa; margin-bottom: 8px;'>",
      get_column("date_display"),
      "</div>",
      "<div style='font-size: 14px; font-weight: 600; color: #ffc864;'>",
      get_column("offset_label"),
      "</div>",
      get_column("alternate_label"),
      "<div style='font-size: 11px; color: #666; margin-top: 6px;'>",
      get_column("zone_label"),
      "</div>",
      get_column("note_label"),
      "</div>"
    )
  ) |>
  add_fill_layer(
    id = "timezone-xinjiang-dual",
    source = xinjiang_timezones,
    fill_color = interpolate(
      column = "utc_offset",
      values = c(-12, -10, -8, -6, -4, -2, 0, 2, 4, 6, 8, 10, 12, 14),
      stops = tz_palette,
      na_color = "#333333"
    ),
    fill_opacity = 0.82,
    hover_options = list(
      fill_opacity = 0.98
    ),
    tooltip = concat(
      "<div style='background: #1a1a2e; padding: 14px 18px; border-radius: 8px; ",
      "border: 1px solid rgba(255, 255, 255, 0.2); font-family: system-ui;'>",
      "<div style='font-size: 32px; font-weight: 700; color: #fff;'>",
      get_column("tooltip_title"),
      "</div>",
      "<div style='font-size: 13px; color: #888; margin-bottom: 8px;'>",
      get_column("primary_time_label"),
      ": ",
      get_column("time_ampm"),
      " ",
      get_column("zone_abbr"),
      "</div>",
      "<div style='font-size: 13px; color: #aaa; margin-bottom: 8px;'>",
      get_column("date_display"),
      "</div>",
      "<div style='font-size: 14px; font-weight: 600; color: #ffc864;'>",
      get_column("offset_label"),
      "</div>",
      get_column("alternate_label"),
      "<div style='font-size: 11px; color: #666; margin-top: 6px;'>",
      get_column("zone_label"),
      "</div>",
      get_column("note_label"),
      "</div>"
    )
  ) |>
  add_line_layer(
    id = "timezone-lines",
    source = timezones,
    line_color = "#ffffff",
    line_width = interpolate(
      property = "zoom",
      values = c(1, 4, 8),
      stops = c(0.25, 0.8, 1.5)
    ),
    line_opacity = 0.35
  ) |>
  add_control(
    html = info_html,
    position = "top-left"
  ) |>
  add_legend(
    legend_title = "Current UTC Offset",
    values = c("-12", "-6", "0", "+6", "+14"),
    colors = c("#1e3a5f", "#5a7a9f", "#f0f4f8", "#ffaa5c", "#8f2200"),
    type = "continuous",
    position = "bottom-left"
  ) |>
  add_navigation_control(position = "top-right") |>
  add_fullscreen_control(position = "top-right")