(defmacro newtimer
  (new java.util.Date))

(def time-signal
  {:output (fn [] {:time (.getTime newtimer)})
   })


Output:

java.lang.IllegalArgumentException: Don't know how to create ISeq from: clojure.lang.Symbol
 at clojure.lang.RT.seqFrom (RT.java:494)
    clojure.lang.RT.seq (RT.java:475)
    clojure.lang.RT.cons (RT.java:561)
    clojure.core$cons.invoke (core.clj:29)
    clojure.core$defmacro$add_implicit_args__3765.invoke (core.clj:434)
    clojure.core$defmacro$add_args__3767.invoke (core.clj:441)
    clojure.core$defmacro.doInvoke (core.clj:442)
    clojure.lang.RestFn.invoke (RestFn.java:467)
    clojure.lang.Var.invoke (Var.java:427)
    clojure.lang.AFn.applyToHelper (AFn.java:172)
    clojure.lang.Var.applyTo (Var.java:532)
    clojure.lang.Compiler.macroexpand1 (Compiler.java:6366)
    clojure.lang.Compiler.macroexpand (Compiler.java:6427)
    clojure.lang.Compiler.eval (Compiler.java:6495)
    clojure.lang.Compiler.load (Compiler.java:6952)
    clojure.lang.Compiler.loadFile (Compiler.java:6912)
    clojure.lang.RT$3.invoke (RT.java:307)
    clj_game.signals.core$eval1141.invoke (NO_SOURCE_FILE:1)
    clojure.lang.Compiler.eval (Compiler.java:6511)
    clojure.lang.Compiler.eval (Compiler.java:6477)
    clojure.core$eval.invoke (core.clj:2797)
    clojure.main$repl$read_eval_print__6405.invoke (main.clj:245)
    clojure.main$repl$fn__6410.invoke (main.clj:266)
    clojure.main$repl.doInvoke (main.clj:266)
    clojure.lang.RestFn.invoke (RestFn.java:1096)
    clojure.tools.nrepl.middleware.interruptible_eval$evaluate$fn__495.invoke (interruptible_eval.clj:57)
    clojure.lang.AFn.applyToHelper (AFn.java:159)
    clojure.lang.AFn.applyTo (AFn.java:151)
    clojure.core$apply.invoke (core.clj:601)
    clojure.core$with_bindings_STAR_.doInvoke (core.clj:1771)
    clojure.lang.RestFn.invoke (RestFn.java:425)
    clojure.tools.nrepl.middleware.interruptible_eval$evaluate.invoke (interruptible_eval.clj:42)
    clojure.tools.nrepl.middleware.interruptible_eval$interruptible_eval$fn__536$fn__538.invoke (interruptible_eval.clj:170)
    clojure.core$comp$fn__4034.invoke (core.clj:2278)
    clojure.tools.nrepl.middleware.interruptible_eval$run_next$fn__529.invoke (interruptible_eval.clj:137)
    clojure.lang.AFn.run (AFn.java:24)
    java.util.concurrent.ThreadPoolExecutor.runWorker (ThreadPoolExecutor.java:1110)
    java.util.concurrent.ThreadPoolExecutor$Worker.run (ThreadPoolExecutor.java:603)
    java.lang.Thread.run (Thread.java:679)