Bukkit

Is the problem reproducible ? If yes, please describe how
1. I don't have SnowManager, and I haven't edited the config, error should appear when starting up(For some reason you can't download SnowManager from the page)

What's the problem ? What should be ?
The plugin can't loadup on startup

What version of Seasons,Craftbukkit, (ProtocolLib) do you use ?
Seasons: Latest
CraftBukkit: 1.8

Do you have an error log ? If yes, please provide it

[15:57:46 ERROR]: Error occurred while disabling Seasons v2.0.3 (Is it up to date?)
java.lang.NoClassDefFoundError: net/minecraft/server/v1_5_R3/World
    at org.rominos2.Seasons.Managers.SnowManager.SeasonsSnowManager.<init>(SeasonsSnowManager.java:40) ~[?:?]
    at org.rominos2.Seasons.Managers.SeasonsManager.initiate(SeasonsManager.java:67) ~[?:?]
    at org.rominos2.Seasons.Seasons.loadWorld(Seasons.java:187) ~[?:?]
    at org.rominos2.Seasons.Seasons.getManager(Seasons.java:198) ~[?:?]
    at org.rominos2.Seasons.SeasonsSettings.saveSave(SeasonsSettings.java:324) ~[?:?]
    at org.rominos2.Seasons.Seasons.onDisable(Seasons.java:94) ~[?:?]
    at org.bukkit.plugin.java.JavaPlugin.setEnabled(JavaPlugin.java:323) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
    at org.bukkit.plugin.java.JavaPluginLoader.disablePlugin(JavaPluginLoader.java:364) [spigot.jar:git-Spigot-db6de12-18fbb24]
    at org.bukkit.plugin.SimplePluginManager.disablePlugin(SimplePluginManager.java:424) [spigot.jar:git-Spigot-db6de12-18fbb24]
    at org.bukkit.plugin.SimplePluginManager.disablePlugins(SimplePluginManager.java:417) [spigot.jar:git-Spigot-db6de12-18fbb24]
    at org.bukkit.craftbukkit.v1_8_R3.CraftServer.disablePlugins(CraftServer.java:336) [spigot.jar:git-Spigot-db6de12-18fbb24]
    at net.minecraft.server.v1_8_R3.MinecraftServer.stop(MinecraftServer.java:460) [spigot.jar:git-Spigot-db6de12-18fbb24]
    at net.minecraft.server.v1_8_R3.MinecraftServer.run(MinecraftServer.java:593) [spigot.jar:git-Spigot-db6de12-18fbb24]
    at java.lang.Thread.run(Thread.java:745) [?:1.7.0_79]
Caused by: java.lang.ClassNotFoundException: net.minecraft.server.v1_5_R3.World
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:91) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
    at org.bukkit.plugin.java.PluginClassLoader.findClass(PluginClassLoader.java:86) ~[spigot.jar:git-Spigot-db6de12-18fbb24]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:425) ~[?:1.7.0_79]
    at java.lang.ClassLoader.loadClass(ClassLoader.java:358) ~[?:1.7.0_79]
    ... 14 more

Please provide the seasons config.

Seasons:
  Summer:
    Visual:
      Textures: ''
      Snow: 0
    ShortName: summer
    Lengths:
      Season: 10.0
      Weather: 0.5
    Percentages:
      Sun: 70
      Rain: 20
      Thunder: 10
    SpecialDays:
      '1': First Day of Summer
      '10': Last Day of Summer
    SnowManagerSpeed:
      Place: 0
      Remove: 0
    Time:
      Day: 14000
      Night: 10000
  Winter:
    Visual:
      Textures: ''
      Snow: 100
    ShortName: winter
    Lengths:
      Season: 5.0
      Weather: 0.5
    Percentages:
      Sun: 30
      Rain: 60
      Thunder: 10
    SpecialDays:
      '1': First Day of Winter
      '3': Mid Winter
      '5': Last Day of Winter
    SnowManagerSpeed:
      Place: 0
      Remove: 0
    Time:
      Day: 14000
      Night: 10000
Properties:
  Active: true
  LogInfo: true
  Resolution:
    Precision: 0.01
    TimeCheck: 20
  Regen:
    Snow: true
    Ice: true
  Messages:
    ChangeMessage: Seasons changes to <name>.
    SeasonsMessage: You're in <name> for another <number> days.
    SpecialDayMessage: It's <name>.
    Weather: The current weather is <name>.
    Color: b
    NotActive: Seasons are not active in this world.
    Sign:
    - <name>
    - <day>/<length>
    - <specialDay>
    ColorList:
      BLACK: '0'
      DARK_BLUE: '1'
      DARK_GREEN: '2'
      DARK_AQUA: '3'
      DARK_RED: '4'
      DARK_PURPLE: '5'
      GOLD: '6'
      GRAY: '7'
      DARK_GRAY: '8'
      BLUE: '9'
      GREEN: a
      AQUA: b
      RED: c
      LIGHT_PURPLE: d
      YELLOW: e
      WHITE: f
      MAGIC: k
      BOLD: l
      STRIKETHROUGH: m
      UNDERLINE: n
      ITALIC: o
      RESET: r
  Debug: false

Any more informations ?
No