`module Timespec : sig ... end`
`module Itimerspec : sig ... end`
`module Timeval : sig ... end`
`module Tm : sig ... end`
`module Itimerval : sig ... end`

`type clock` = `[`

`|` ``Realtime`
`|` ``Monotonic`
`|` ``Process_cputime`
`|` ``Thread_cputime`

`]`

`val asctime : Tm.t -> string`
`val clock_getres : clock -> Timespec.t`
`val clock_gettime : clock -> Timespec.t`
`val clock_settime : clock -> Timespec.t -> unit`
`val ctime : int64 -> string`
`val gmtime : int64 -> Tm.t`
`val localtime : int64 -> Tm.t`
`val mktime : Tm.t -> int64`
`val nanosleep : Timespec.t -> unit`

`type itimer` = `[`

`|` ``Real`
`|` ``Virtual`
`|` ``Prof`

`]`

`val getitimer : itimer -> Itimerval.t`
`val setitimer : itimer -> Itimerval.t -> Itimerval.t`
`val gettimeofday : unit -> Timeval.t`
`val select : Unix.file_descr list -> Unix.file_descr list -> Unix.file_descr list -> Timeval.t option -> Unix.file_descr list * Unix.file_descr list * Unix.file_descr list`
`val utimes : string -> Timeval.t -> unit`