The World Info interface is used to get even more information out of an IWorld object.

It might be required for you to import the package if you encounter any issues, so better be safe than sorry and add the import.
import crafttweaker.world.IWorldInfo;

ZenGetter	ZenMethod	Return Type
ZenGetter commandsAllowed	ZenMethod isCommandsAllowed()	Return Type bool
ZenGetter borderCenterX	ZenMethod getBorderCenterX()	Return Type double
ZenGetter borderCenterZ	ZenMethod getBorderCenterZ()	Return Type double
ZenGetter borderDamagePerBlock	ZenMethod getBorderDamagePerBlock()	Return Type double
ZenGetter borderSafeZone	ZenMethod getBorderSafeZone()	Return Type double
ZenGetter borderSize	ZenMethod getBorderSize()	Return Type double
ZenGetter borderWarningDistance	ZenMethod getBorderWarningDistance()	Return Type int
ZenGetter borderWarningTime	ZenMethod getBorderWarningTime()	Return Type int
ZenGetter cleanWeatherTime	ZenMethod getCleanWeatherTime()	Return Type double
ZenGetter difficulty	ZenMethod getDifficulty()	Return Type string
ZenGetter generatorOptions	ZenMethod getGeneratorOptions()	Return Type string
ZenGetter lastTimePlayed	ZenMethod getLastTimePlayed()	Return Type long
ZenGetter rainTime	ZenMethod getRainTime()	Return Type int
ZenGetter saveVersion	ZenMethod getSaveVersion()	Return Type int
ZenGetter seed	ZenMethod getSeed()	Return Type long
ZenGetter spawnX	ZenMethod getSpawnX()	Return Type int
ZenGetter spawnY	ZenMethod getSpawnY()	Return Type int
ZenGetter spawnZ	ZenMethod getSpawnZ()	Return Type int
ZenGetter thunderTime	ZenMethod getThunderTime()	Return Type int
ZenGetter versionId	ZenMethod getVersionId()	Return Type int
ZenGetter versionName	ZenMethod getVersionName()	Return Type string
ZenGetter worldName	ZenMethod getWorldName()	Return Type string
ZenGetter worldTotalTime	ZenMethod getWorldTotalTime()	Return Type long
ZenGetter boderLerpTarget	ZenMethod getBoderLerpTarget()	Return Type double
ZenGetter boderLerpTime	ZenMethod getBoderLerpTime()	Return Type long
ZenGetter difficultyLocked	ZenMethod isDifficultyLocked()	Return Type bool
ZenGetter hardcoreModeEnabled	ZenMethod isHardcoreModeEnabled()	Return Type bool
ZenGetter initialized	ZenMethod isInitialized()	Return Type bool
ZenGetter mapFeaturesEnabled	ZenMethod isMapFeaturesEnabled()	Return Type bool
ZenGetter thundering	ZenMethod isThundering()	Return Type bool
ZenGetter versionSnapshot	ZenMethod isVersionSnapshot()	Return Type bool