diff --git a/README.md b/README.md
index 40397ee..b8918c4 100644
--- a/README.md
+++ b/README.md
@@ -1,3 +1,16 @@
-# sunset
+# Calculating sunrise/sunset times for a given location
+
+Based on algorithm by United Stated Naval Observatory, Washington
+
+https://edwilliams.org/sunrise_sunset_algorithm.htm
+
+## Usage
+
+```
+local sun = require('sun')
+
+sunrise, sunset,length = sun.get('2025-05-25 21:00:14+03',54.314192, 48.403132)
+
+```
+
 
-Калькулятор времен восхода и заката Солнца по классическому алгоритму 
\ No newline at end of file
diff --git a/sun.lua b/sun.lua
new file mode 100644
index 0000000..5ed7256
--- /dev/null
+++ b/sun.lua
@@ -0,0 +1,106 @@
+-- Module for calculating sunrise/sunset times for a given location
+-- Based on algorithm by United Stated Naval Observatory, Washington
+-- Link: https://edwilliams.org/sunrise_sunset_algorithm.htm
+-- @author Alexander Yakushev
+-- @author Alexander Pavlov (Zoviet)
+-- @license CC0 http://creativecommons.org/about/cc0
+
+local date = require("date")
+
+local _M = {}
+
+local cosH_rise,RA_rise,cosH_set,RA_set,sunrise,sunset,length
+
+local current_time = nil
+local srs_args
+local rad = math.rad
+local deg = math.deg
+local floor = math.floor
+local frac = function(n) return n - floor(n) end
+local cos = function(d) return math.cos(rad(d)) end
+local acos = function(d) return deg(math.acos(d)) end
+local sin = function(d) return math.sin(rad(d)) end
+local asin = function(d) return deg(math.asin(d)) end
+local tan = function(d) return math.tan(rad(d)) end
+local atan = function(d) return deg(math.atan(d)) end
+
+local function days(utc)
+	local UT = 0
+	if utc then 
+		UT = tonumber(string.match(utc, '%+(%d+)')) or 0
+		utc = date(utc) 		
+	else
+		utc = date():toutc()
+	end
+	return utc:getyearday(), UT
+end
+
+local function fit_into_range(val, min, max)
+   local range = max - min
+   local count
+   if val < min then
+      count = floor((min - val) / range) + 1
+      return val + count * range
+   elseif val >= max then
+      count = floor((val - max) / range) + 1
+      return val - count * range
+   else
+      return val
+   end
+end
+
+local function calc(t,lat,lon,zenith)
+	local M = (0.9856 * t) - 3.289
+	local L = fit_into_range(M + (1.916 * sin(M)) + (0.020 * sin(2 * M)) + 282.634, 0, 360)
+	local RA = fit_into_range(atan(0.91764 * tan(L)), 0, 360) -- Прямое восхождение Солнца
+	local Lquadrant  = floor(L / 90) * 90
+	local RAquadrant = floor(RA / 90) * 90
+	RA = RA + Lquadrant - RAquadrant
+	RA = RA / 15
+	local sinDec = 0.39782 * sin(L)
+	local cosDec = cos(asin(sinDec))
+	local cosH = (cos(zenith) - (sinDec * sin(lat))) / (cosDec * cos(lon))
+	return cosH,RA
+end
+
+local function sun(utc,lat,lon,zenith)
+	zenith = zenith or 90.5--90.83
+	local days,UT = days(utc)	
+	local lng_hour = lon/15
+	local t_rise, t_set	
+    local t_rise = days + ((6 - lng_hour) / 24)
+    local t_set = days + ((18 - lng_hour) / 24)
+    cosH_rise,RA_rise = calc(t_rise,lat,lon,zenith) -- часовой угол
+	cosH_set,RA_set = calc(t_set,lat,lon,zenith)
+	local H_rise,H_set,sunrise_i,sunset_i
+	if cosH_rise > 1 then sunrise = nil 
+	else
+		H_rise = (360 - acos(cosH_rise))/15
+		sunrise = H_rise + RA_rise - (0.06571 * t_rise) - 6.622	
+		sunrise_i = fit_into_range(sunrise - lng_hour, 0, 24) + UT
+		sunrise = date():sethours(0, 0, 0):addhours(sunrise_i):fmt('%Y-%m-%d %T')
+	end
+	if cosH_set < -1 then sunset = nil
+	else
+		H_set = acos(cosH_set)/15
+		sunset = H_set + RA_set - (0.06571 * t_set) - 6.622	
+		sunset_i = fit_into_range(sunset - lng_hour, 0, 24) + UT
+		sunset = date():sethours(0, 0, 0):addhours(sunset_i):fmt('%Y-%m-%d %T')
+	end
+	if sunset and sunrise then length = sunset_i - sunrise_i end
+end
+
+--Sun's zenith for sunrise/sunset:
+
+--	zenith:              
+--  offical      = 90 degrees 50'
+--  civil        = 96 degrees
+-- nautical     = 102 degrees
+-- astronomical = 108 degrees
+
+function _M.get(utc,lat,lon,zenith)
+	sun(utc,lat,lon,zenith)
+	return sunrise, sunset,length
+end
+
+return _M
diff --git a/test.lua b/test.lua
new file mode 100644
index 0000000..a072ec8
--- /dev/null
+++ b/test.lua
@@ -0,0 +1,4 @@
+local sun = require('sun')
+
+print(sun.get('2025-05-25 21:00:14+03',54.314192, 48.403132))
+