diff --git a/app.js b/app.js
index 455ab24..1fcb0c8 100644
--- a/app.js
+++ b/app.js
@@ -9,7 +9,7 @@ const {port} = require('./config')
 const app = require('express')()
 const helmet = require('helmet')
 const routes = require('./src/routes')
-const { errors } = require('celebrate')
+const {errors} = require('celebrate')
 const body_parser = require('body-parser')
 const {request_logger, error_logger} = require('./src/middlewares/logger')
 const {options, cors} = require('./src/middlewares/cors')
diff --git a/lib b/lib
index b3fa29e..2daac94 160000
--- a/lib
+++ b/lib
@@ -1 +1 @@
-Subproject commit b3fa29e4c5034524a15c57ff9cfcbf2b142032d3
+Subproject commit 2daac94e9224762fbec7578ae5b964e6d413c691
diff --git a/src/controllers/session.js b/src/controllers/session.js
index 7abf6db..9bc4692 100644
--- a/src/controllers/session.js
+++ b/src/controllers/session.js
@@ -5,35 +5,34 @@ const {get_fastest_session_server, run_session} = require('../modules/session_se
 const create_session = async (req, res, next) => {
     const {title} = req.body
 
-    var free_servers = await database.get_free_session_servers(title)
+    let free_servers = await database.get_free_session_servers(title)
 
     if (!free_servers) {
         next(new not_found_error('no free session server or title not exists'))
         return
     }
 
-    var session_server = await get_fastest_session_server(free_servers)
+    let session_server = await get_fastest_session_server(free_servers)
     
     if (!session_server) {
         next(new not_found_error('all session servers are not available'))
         return
     }
 
-    var session_id = await database.generate_session_id()
+    let session_id = await database.generate_session_id()
     if (!session_id) {
         next(new not_found_error('can not generate session id'))
         return
     }
 
-    var websocket_url = await run_session(session_server.url, session_id, title)
+    let websocket_url = await run_session(session_server.url, session_id, title)
 
     if (!websocket_url) {
         next(new not_found_error('can not run session'))
         return
     }
     
-    var add_active_session_result = await database.add_active_session(session_server.url, session_id, websocket_url)
-    await database.add_session_to_history(session_server.url, session_id, websocket_url)
+    let add_active_session_result = await database.add_active_session(title, session_server.url, session_id, websocket_url)
 
     if (!add_active_session_result) {
         next(new not_found_error('add_active_session error'))
@@ -43,7 +42,7 @@ const create_session = async (req, res, next) => {
 }
 
 const connect_session = async (req, res, next) => {
-    var websocket_url = await database.get_session_websocket_url(req.query.session_id)
+    let websocket_url = await database.get_session_websocket_url(req.query.session_id)
     if (!websocket_url) {
         next(new not_found_error('session not exists'))
         return
diff --git a/src/controllers/session_server.js b/src/controllers/session_server.js
index 3b04a0e..0cf8d23 100644
--- a/src/controllers/session_server.js
+++ b/src/controllers/session_server.js
@@ -2,12 +2,42 @@ const server_error = require('../../lib/src/http/errors/server_error')
 const database = require('../database/database')
 
 const session_closed = async (req, res, next) => {
-    var remove_result = await database.remove_active_session(req.body.session_id)
+
+    const {
+        session_id,
+        title,
+        max_uniq_users,
+        users_at_close,
+        time,
+        unix_timestamp,
+        time_end,
+        unix_timestamp_end
+    } = req.body
+
+    let active_session = await database.get_active_session(session_id)
+    if (active_session) {
+        await database.add_session_to_history(
+            session_id,
+            title,
+            active_session.server_url,
+            active_session.websocket_url,
+            max_uniq_users,
+            users_at_close,
+            time,
+            unix_timestamp,
+            time_end,
+            unix_timestamp_end
+        )
+    }
+
+    let remove_result = await database.remove_active_session(session_id)
+
     if (!remove_result) {
         next(new server_error('remove session error'))
         return
     }
-    res.json({message:"removed"})
+
+    res.json({message:"successfully removed"})
 }
 
 module.exports = {
diff --git a/src/controllers/status.js b/src/controllers/status.js
index 195d3ff..b8ef0e7 100644
--- a/src/controllers/status.js
+++ b/src/controllers/status.js
@@ -6,7 +6,7 @@ const {ping_session_server} = require('../modules/session_server.js')
 const max_response_timeout = 500
 
 const validate_url = async (domain) => {
-    var options = {
+    let options = {
         url: domain,
         method: "GET",
         path: '/',
diff --git a/src/controllers/title.js b/src/controllers/title.js
index 1940496..ed26008 100644
--- a/src/controllers/title.js
+++ b/src/controllers/title.js
@@ -2,7 +2,7 @@ const database = require('../database/database.js')
 const not_found_error = require('../../lib/src/http/errors/not_found_error')
 
 const get_titles = async (req, res, next) => {
-    var titles = await database.get_titles(req.query.start, req.query.count)
+    let titles = await database.get_titles(req.query.start, req.query.count)
      
     if (!titles) {
         next(new not_found_error('titles not found'))
@@ -13,7 +13,7 @@ const get_titles = async (req, res, next) => {
 }
 
 const get_titles_for_language = async (req, res, next) => {
-    var titles = await database.get_titles_for_language(req.query.start, req.query.count, req.query.language.toLowerCase())
+    let titles = await database.get_titles_for_language(req.query.start, req.query.count, req.query.language.toLowerCase())
 
     if (!titles) {
         next(new not_found_error('titles not found'))
@@ -25,7 +25,7 @@ const get_titles_for_language = async (req, res, next) => {
 
 const get_private_titles = async (req, res, next) => {
     const {key} = req.query
-    var titles = await database.get_private_titles_with_key(key)
+    let titles = await database.get_private_titles_with_key(key)
 
     if (!titles) {
         next(new not_found_error('title not found'))
diff --git a/src/database/database.js b/src/database/database.js
index 54ec185..fbc594f 100644
--- a/src/database/database.js
+++ b/src/database/database.js
@@ -1,7 +1,7 @@
 const { MongoClient } = require("mongodb")
 const { database_url, database_name } = require('../../config')
 const crypto = require("crypto")
-const time = require('../modules/time')
+const time = require('../../lib/src/time')
 let max_database_connection_timeout = 1000
 
 const client = new MongoClient(database_url, {
@@ -22,50 +22,50 @@ const get_db = async () => {
 }
 
 const get_titles = async (start, count) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
-    var titles = await db.collection('title').find().skip(parseInt(start)).limit(parseInt(count)).toArray()
+    let titles = await db.collection('title').find().skip(parseInt(start)).limit(parseInt(count)).toArray()
     return (!titles.length) ? null : titles
 }
 
 const get_titles_for_language = async (start, count, language) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
-    var titles = await db.collection('title').find({language:language}).skip(parseInt(start)).limit(parseInt(count)).toArray()
+    let titles = await db.collection('title').find({language:language}).skip(parseInt(start)).limit(parseInt(count)).toArray()
     return (!titles.length) ? null : titles
 }
 
 const get_private_titles_with_key = async (key) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
-    var titles = await db.collection('private_title').find({key:key}).toArray()
+    let titles = await db.collection('private_title').find({key:key}).toArray()
     return (!titles.length) ? null : titles
 }
 
 const get_free_session_servers = async (title) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
 
-    var servers = await db.collection('session_server').find({title:title}).toArray()
+    let servers = await db.collection('session_server').find({title:title}).toArray()
 
     if (!servers.length) {
         return null
     }
 
-    var active_session = db.collection('active_session')
+    let active_session = db.collection('active_session')
     
-    var free_servers = []
+    let free_servers = []
 
     for (const server of servers) {
-        var sessions = await active_session.find({server_url:server.url}).toArray()
+        let sessions = await active_session.find({server_url:server.url}).toArray()
         if (server.limit > sessions.length) {
             free_servers.push(server)
         }
@@ -73,33 +73,35 @@ const get_free_session_servers = async (title) => {
     return (free_servers.length) ? free_servers : null
 }
 
-const add_active_session = async (server_url, session_id, websocket_url) => {
-    var db = await get_db()
+const add_active_session = async (title, server_url, session_id, websocket_url) => {
+    let db = await get_db()
     if (!db) {
         return false
     }
 
-    var active_session = db.collection('active_session')
+    let active_session = db.collection('active_session')
 
     await active_session.insertOne({
+        title: title,
         server_url: server_url,
         session_id: session_id,
         websocket_url: websocket_url
     })
+
     return true
 }
 
 const generate_session_id = async () => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
 
-    var active_session = db.collection('active_session')
-    var session_id = {}
+    let active_session = db.collection('active_session')
+    let session_id = {}
 
-    var max_id_len = 6
-    var sessions_with_id = 0
+    let max_id_len = 6
+    let sessions_with_id = 0
     while(true) {
         session_id = crypto.randomBytes(max_id_len/2).toString('hex').toUpperCase()
         sessions_with_id = await active_session.find({session_id:session_id}).toArray().length
@@ -109,8 +111,18 @@ const generate_session_id = async () => {
     }
 }
 
+const get_active_session = async (session_id) => {
+    let db = await get_db()
+    if (!db) {
+        return null
+    }
+    
+    let active_session = await db.collection('active_session').findOne({session_id:session_id})
+    return active_session
+}
+
 const remove_active_session = async (session_id) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return false
     }
@@ -120,12 +132,12 @@ const remove_active_session = async (session_id) => {
 }
 
 const get_session_websocket_url = async (session_id) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
-    var active_session = db.collection('active_session')
-    var session = await active_session.findOne({session_id:session_id})
+    let active_session = db.collection('active_session')
+    let session = await active_session.findOne({session_id:session_id})
     if (!session) {
         return null
     }
@@ -133,21 +145,21 @@ const get_session_websocket_url = async (session_id) => {
 }
 
 const get_statuses = async () => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
-    var statuses = await db.collection('status').find().toArray()
+    let statuses = await db.collection('status').find().toArray()
     return (!statuses.length) ? null : statuses
 }
 
 const get_all_session_servers = async () => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
 
-    var servers = await db.collection('session_server').find().toArray()
+    let servers = await db.collection('session_server').find().toArray()
 
     if (!servers.length) {
         return null
@@ -156,33 +168,33 @@ const get_all_session_servers = async () => {
 }
 
 const add_error = async (error_message) => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return false
     }
 
-    var error_collection = db.collection('error')
+    let error_collection = db.collection('error_history')
 
-    await error_collection.insertOne({error_message:error_message, time: time.get_date_time()})
+    await error_collection.insertOne({error_message:error_message, time: time.get_date_time(), unix_timestamp: time.get_unix_timestamp()})
     return true
 }
 
 const get_errors = async () => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
-    var errors = await db.collection('error').find().toArray()
+    let errors = await db.collection('error_history').find().toArray()
     return (!errors.length) ? null : errors
 }
 
 const get_all_active_sessions = async () => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
 
-    var active_sessions = await db.collection('active_session').find().toArray()
+    let active_sessions = await db.collection('active_session').find().toArray()
 
     if (!active_sessions.length) {
         return null
@@ -190,30 +202,50 @@ const get_all_active_sessions = async () => {
     return active_sessions
 }
 
-const add_session_to_history = async (server_url, session_id, websocket_url) => {
-    var db = await get_db()
+const add_session_to_history = async (session_id, 
+    title, 
+    server_url, 
+    websocket_url, 
+    max_uniq_users, 
+    users_at_close, 
+    time_start, 
+    unix_timestamp_start, 
+    time_end, 
+    unix_timestamp_end
+    ) => {
+
+    let db = await get_db()
     if (!db) {
         return false
     }
 
-    var session_history = db.collection('session_history')
+    let session_history = db.collection('session_history')
 
+    let duration_in_seconds = unix_timestamp_end - unix_timestamp_start
     await session_history.insertOne({
-        server_url: server_url,
         session_id: session_id,
+        title: title,
+        server_url: server_url,
         websocket_url: websocket_url,
-        time: time.get_date_time()
+        max_uniq_users: max_uniq_users,
+        users_at_close: users_at_close,
+        time_start: time_start,
+        unix_timestamp_start: unix_timestamp_start,
+        time_end: time_end,
+        unix_timestamp_end: unix_timestamp_end,
+        duration_in_seconds: duration_in_seconds,
+        duration_in_minutes: duration_in_seconds / 60
     })
     return true
 }
 
 const get_all_session_history = async () => {
-    var db = await get_db()
+    let db = await get_db()
     if (!db) {
         return null
     }
 
-    var session_history = await db.collection('session_history').find().toArray()
+    let session_history = await db.collection('session_history').find().toArray()
 
     if (!session_history.length) {
         return null
@@ -227,6 +259,7 @@ module.exports = {
     add_active_session,
     generate_session_id,
     remove_active_session,
+    get_active_session,
     get_session_websocket_url,
     get_titles_for_language,
     get_private_titles_with_key,
diff --git a/src/middlewares/logger.js b/src/middlewares/logger.js
index c45ddd4..e65e3d6 100644
--- a/src/middlewares/logger.js
+++ b/src/middlewares/logger.js
@@ -4,7 +4,7 @@ const {log_path} = require('../../config')
 const logger_runtime = new _logger(log_path)
 
 const request_logger = (req, res, next) => {
-    var {url} = req
+    let {url} = req
     logger_runtime.log(url)
     next()
 }
diff --git a/src/modules/session_server.js b/src/modules/session_server.js
index 5d6b9e6..aef2f3b 100644
--- a/src/modules/session_server.js
+++ b/src/modules/session_server.js
@@ -1,11 +1,11 @@
-var request = require('request')
+let request = require('request')
 const max_response_timeout = 2000
 const max_run_session_timeout = 20000
 
 
 const ping_session_server = async (url) => {
 
-    var options = {
+    let options = {
         url: url + '/ping',
         method: "GET",
         timeout: max_response_timeout
@@ -25,7 +25,7 @@ const ping_session_server = async (url) => {
 }
 
 const get_fastest_session_server = async (free_servers) => {
-    var fastest_server = null
+    let fastest_server = null
 
     Promise.all(free_servers.map(async (server) => {
         const is_working = await ping_session_server(server.url)
@@ -36,8 +36,8 @@ const get_fastest_session_server = async (free_servers) => {
         }
     }))
 
-    var timeout_count = 0
-    var check_times = 100
+    let timeout_count = 0
+    let check_times = 100
 
     while (true) {
         ++timeout_count
@@ -53,7 +53,7 @@ const get_fastest_session_server = async (free_servers) => {
 }
 
 const run_session = async (server_url, session_id, title) => {
-    var options = {
+    let options = {
         url: server_url + '/session/run',
         method: "POST",
         timeout: max_run_session_timeout,
@@ -81,7 +81,7 @@ const run_session = async (server_url, session_id, title) => {
 
 const get_overal_status = async (url) => {
 
-    var options = {
+    let options = {
         url: url + '/get_overal_status',
         method: "GET",
         timeout: max_response_timeout
diff --git a/src/modules/time.js b/src/modules/time.js
deleted file mode 100644
index 69187a6..0000000
--- a/src/modules/time.js
+++ /dev/null
@@ -1,14 +0,0 @@
-const get_date_time = () => {
-    let currentdate = new Date(); 
-    let datetime = currentdate.getDate() + "/"
-                + (currentdate.getMonth()+1)  + "/" 
-                + currentdate.getFullYear() + " @ "  
-                + currentdate.getHours() + ":"  
-                + currentdate.getMinutes() + ":" 
-                + currentdate.getSeconds()
-    return datetime
-}
-
-module.exports = {
-    get_date_time
-}
\ No newline at end of file
diff --git a/src/routes/session_server.js b/src/routes/session_server.js
index f79553d..8a541cb 100644
--- a/src/routes/session_server.js
+++ b/src/routes/session_server.js
@@ -4,7 +4,14 @@ const { celebrate, Joi, Segments} = require('celebrate')
 
 router.post('/session_closed', celebrate({
     [Segments.BODY]: Joi.object().keys({
-        session_id: Joi.string().required()
+        session_id: Joi.string().required(),
+        title: Joi.string().required(),
+        max_uniq_users: Joi.number().required(),
+        users_at_close: Joi.number().required(),
+        time: Joi.string().required(),
+        unix_timestamp: Joi.number().required(),
+        time_end: Joi.string().required(),
+        unix_timestamp_end: Joi.number().required()
     })
 }), session_closed)